STANDARD SPECIFICATIONS AND CODE OF PRACTICE FOR … · 2015. 1. 12. · IRC:6-2014 Firstpublished...

IRC:6-2014

STANDARD SPECIFICATIONSAND CODE OF PRACTICEFOR ROAD BRIDGES

SECTION : II

LOADS AND STRESSES(Revised Edition)

(Incorporating All Amendments and Errata published upto December, 2013)

INDIAN ROADS CONGRESS2014

IRC:6-2014

STANDARD SPECIFICATIONS

AND

CODE OF PRACTICE FOR

ROAD BRIDGES

SECTION: II

LOADS AND STRESSES

(Revised Edition)

(Incorporating All Amendments and Errata published upto December, 2013)

Published by

INDIAN ROADS CONGRESS

Kama Koti Marg

Sector-6, R.K. PuramNew Delhi-110022

JANUARY, 2014

Price ? 700/-

(Packing and postage charges extra)

IRC:6-2014

First published December, 1958

Reprinted May, lybz

Reprinted September, 19dv3

Second Revision uctober, iyD4

Third Revision Metric units . uctoDer, nyoD

Reprinted uctoDer, lyb/

Reprinted Novemoer, lyoy

Reprinted March, 1972 (incorporates Amendment No. 1-Nov. 1971)

Reprinted February, 1974 (incorporates Amendment No. 2-Nov. 1972)

Reprinted August 1974 (incorporates Amendment No. 3-April 1974 and No. 4-August 1974)

Reprinted juiy, ly/ / (incorporaies Amenament NO. o-ucioDer, ly/b)

Reprinted oepiemDer, lyo i (incorporaies me cnanges as given in ueiaii in me lasi two suD-paras

OT inirouuciion ai pctge o)

Reprinted November, 1985

Reprinted beptember, lyyu

Reprinted 1 y^ 1 1 y^ r"\ / T CI Cj AJanuary, iyy4

Reprinted \ t~i t t ^ r \ J "1007January, lyy/

Reprinted iviarcn, lyyy

Fourth Revision uecemDer, ûuu

Reprinted April, 2002 (Incorporates amended Fig. 5 at page 23)

Reprinted August, 2004 (Incorporates up-to-date Amendments)Reprinted August, zuuo

Kepriniea Ar\r'i\ or\r\RApril, ûudReprinted September, 2009 (Incorporates Amendment No. 6)

Fifth Revision November, 2010

Revised Edition January, 2014 (Incorporating all Amendments and Errata Published upto

December, 2013)

(All Rights Reserved. No Part of this Publication shall be reproduced,

translated or transmitted in any form or by any means without the

permission of the Indian Roads Congress)

Printed by India Offset Press, Delhi-1 10064

(1000 Copies)

IRC:6-2014

CONTENTS

Page No.

Personnel of the Bridges Specifications and Standards Committee (i)

Introduction 1

Scope 3

201 Classification 3

202 Loads, Forces and Stresses 4

203 Dead Load 5

204 Live Loads ' 8

205 Reduction in the Longitduinal Effect on Bridges Accommodating 19

more than Two Traffic Lanes

206 Foot Over Bridges, Footway, Kerb, Railings, Parapet and Crash Barriers 19

207 Tramway Loading 23

208 Impact 24

209 Wind Load 27

210 Horizontal Forces due to Water Currents 34

211 Longitudinal Forces 37

212 Centrifugal Forces 40

213 Buoyancy 41

214 - Earth Pressure 41

215 Temperature . , , 42

216 Deformation Stresses (for steel bridges only) 46

217 Secondary Stresses 47

218 Erection Stresses and Construction Loads 47

219 Seismic Force 48

220 Barge Impact on Bridges 59

221 Snow Load 64

222 Vehicle Collision Loads on Supports of Bridges, Flyover Supports and 65

Footover Bridges

223 Indeterminate Structures and Composite Structures 66

ANNEXURES

Digitized by the Internet Arch ive

in 2014

https ://arch ive .0rg/detai Is/govlawircy201406

IRC:6-2014

PERSONNEL OF THE BRIDGES SPECIFICATIONS AND STANDARDS COMMITTEE(As on e**^ January, 2014)

1. Kandasamy, C.

(Convenor

)

2. Patankar, V.L.

(Co-Convenor)

3. Pathak, A.P.

(Member-Secretary)

4. Agrawal, K.N.

5. Alinnchandani, C.R.

6. Arora, H.C.

7. Bagish, Dr. B.P.

8. Bandyopadhyay, Dr. N.

9. Bandyopadhyay, Dr. T.K

10. Banerjee, A.K.

11. Banerjee, T.B.

12. Basa.Ashok

13. Bhasin, P.C.

14. Bhowmick, Alok

15. Bongirwar, P.L.

16. Dhodapkar, A.N.

17. Ghoshal,A.

18. Joglekar, S.G.

19. Kand,,C.V.

20. Koshi, Ninan

21. Kumar, Ashok

22. Kumar, Prafulla

23. Kumar, Vijay

24. Manjure, P.Y.

25. Mukherjee, M.K.

26. Nagpal,A.K.

27. Narain,A.D.

Director General (RD) & Spl. Secy, to Govt, of India, Ministry of RoadTransport and Highways, Transport Bhavan, New Delhi

Addl. Director General, Ministry of Road Transport and Highways

Transport Bhavan, New Delhi

Chief Engineer (B) S&R, (Ministry of Road Transport & Highways,

Transport Bhavan, New Delhi

Members

DG(W), CPWD (Retd.) Ghaziabad

Chairman & Managing Director, STUP Consultants (P) Ltd., Mumbai

Chief Engineer (Retd.) MORTH, New Delhi

C-2/2013, Vasant Kunj, 0pp. D.RS. New Delhi

Director, Stup Consultants (P) Ltd. New Delhi

Joint Director General (Retd.) INSDAG, Kolkata

Chief Engineer (Retd.) MoRT&H, New Delhi


Director (Tech.) B. Engineers & Builders Ltd., Bhubaneswar

ADG (B), (Retd.), MoRT&H, New Delhi

Managing Director, Bridge & Structural Engg. Consultants (P) Ltd.,

Noida

Advisor, L&T, Mumbai


Director and Vice President, STUP Consultants (P) Ltd. Kolkata

Vice President, STUP Consultants (P) Ltd. , Mumbai

Chief Engineer (Retd.), MP, PWD Bhopal

DG(RD) & Addl. Secy., (Retd) MOST New Delhi

Chief Enginee (Retd.), MoRT&H, New Delhi

DG (RD) & AS, MoRT&H (Retd.) New Delhi

E-in-Chief (Retd.) UP, PWD,

Director, Freyssinet Prestressed Concrete Co. Mumbai


Prof. NT, New Delhi

DG (RD) & AS, MoRT&H (Retd.) New Delhi

(i)

IRC:6-2014

Zo. Ninan, K.b. unieT engineer (Keta.) MoKi oiM New ueini

randey, K.i\. unieT engineer (rianning), mok i oiH, New uelni

30. Parameswaran, Dr. Lakshmy Chief Scientist (BAS), CRRI, New Delhi

31. Raizada, Pratap S. Vice President (Corporate Affairs). Gammon India Ltd. Mumbai

32. Rao, Dr. M.V.B. A-181, Sarita Vihar, New Delh

33. Roy, Dr. B.C. Senior Executive Director, M/s. Consulting Engg. Services India (Pvt.)

Lia. ourgaon

oana, ur. o.k executive uirecior L/onsiruma L/Onsuiiancy (^r) Lia. iviumoai

35. Sharan, G. DG (RD) & Spl. Secy (Retd.) MoRT&H, New Dellhi

36. Sharma, R.S. Chief Engineer (Retd.) MoRT&H, New Delhi

37. Sinha, N.K. DG(RD) & SS, (Retd.) MoRT&H New Delhi

38. Subbarao, Dr. Harshavardhan Chairman & Managing Director, Construma Consultancy (P) Ltd.

IVIUl 1 lUdI

lanQon, ivianesn rroi. Managing uirecior, lanoon uonsuiianis [r) LTa.,iNew ueini

/I n1 nanaavan, rv.d. oniei engineer ^Keia. j iviok i dkn. New ueini

41. Velayutham,, V. DG (RD) & SS (Retd.) MoRT&H, New Delhi

42. Viswanathan, T. 7046, Sector B, Pocket 10 , Vasant Kunj ,New Delhi

43. The Executive Director (B&S) RDSO, Lucknow

44. The Director and Head, (Civil

Engg.),

Bureau of Indian Standards, New Delhi

Corresponding Members

1. Raima, Dr. V.K. Consultant (W.B.)

2. Singh, R.B. Director, Projects Consulting India (P) Ltd. New Delhi

Ex-Officio Members

1. Kandasamy, C. Director General (Road Development) & Special Secretary, MoRT&Hand President, Indian Roads Congress, New Delhi

2. Prasad, Vishnu Shankar Secretary General, Indian Roads Congress, New Delhi

(ii)

STANDARD SPECIFICATIONS AND CODE OFPRACTICE FOR ROAD BRIDGES

IRC:6-2014

INTRODUCTIONThe brief history of the Bridge Code given in the Introduction to Section I "General Features of

Design" generally applies to Section 1 1 also. The draft of Section 1 1 for "Loads and Stresses", as

discussed at Jaipur Session of the Indian Roads Congress in 1 946, was considered further in

a number of meetings of the Bridges Committee for finalisation. In the years 1957 and 1958,

the work of finalising the draft was pushed on vigorously by the Bridges Committee.

In the Bridges Committee meeting held at Bombay in August 1958, all the commentsreceived till then on the different clauses of this Section were disposed off finally and a

drafting Committee consisting of S/Shri S.B. Joshi, K.K. Nambiar, K.F. Antia and S.K. Ghoshwas appointed to work in conjunction with the officers of the Roads Wing of the Ministry for

finalising this Section.

This Committee at its meeting held at New Delhi in September 1958 and later through

correspondences finalized Section II of the Bridge Code, which was printed in 1958 and

reprinted in 1962 and 1963.

The Second Revision of Section II of the IRC:6 Code (1964 edition) included all the

amendments, additions and alterations made by the Bridges Specifications and Standards

(BSS) Committee in their meetings held from time to time.

The Executive Committee of the Indian Roads Congress approved the publication of the

Third Revision in metric units in 1966.

The Fourth Revision of Section II of the Code (2000 Edition) included all the amendments,additions and alterations made by the BSS Committee in their meetings held from time to

time and was reprinted in 2002 with Amendment No.1, reprinted in 2004 with AmendmentNo. 2 and again reprinted in 2006 with Amendment Nos. 3, 4 and 5.

The Bridges Specifications and Standards Committee and the IRC Council at various meetings

approved certain amendments viz. Amendment No. 6 of November 2006 relating to Sub-

Clauses 218.2, 222.5, 207.4 and Appendix-2, Amendment No. 7 of February 2007 relating to

Sub-Clauses of 213.7, Note 4 of Appendix-I and 218.3, Amendment No. 8 of January 2008relating to Sub-Clauses 214.2(a), 214.5.1.1 and 214.5.2 and new Clause 212 on Wind load.

As approved by the BSS Committee and IRC Council in 2008, the Amendment No. 9 of May2009 incorporating changes to Clauses 202.3, 208, 209.7 and 218.5 and Combination of

Loads for limit state design of bridges has been introduced in Appendix-3, apart from the

new Clause 222 on Seismic Force for design of bridges.

The Bridges Specifications and Standards Committee in its meeting held on 26th October,

2009 further approved certain modifications to Clause 210.1, 202.3, 205, Note below Clause

208, 209.1, 209.4, 209.7, 222.5.5, Table 8, Note below Table 8, 222.8, 222.9, Table 1 anddeletion of Clause 213.8, 214.5.1.2 and Note below para 8 of Appendix-3. The Convenorof B-2 Committee was authorized to incorporate these modifications in the draft for Fifth

Revision of IRC:6, in the light of the comments of some members. The Executive Committee,

1

IRC:6-2014

in its meeting held on 31st October, 2009, and the IRC Council in its ^89^'" meeting held on14th November, 2009 at Patna approved publishing of the Fifth Revision of IRC: 6.

The current Revised Edition of IRC:6 includes all the amendments and errata published from

time to time upto December, 2013.

The Revised Edition of IRC:6 was approved by the Bridges Specifications and Standards

Committee in its meeting held on 06.01.2014 and Executive Committee meeting held on

09.01.2014 for publishing.

The personnel of the Loads and Stresses Committee (B-2) is given below:

Banerjee, A.K.

Dhodapkar, A.N.

Parameswaran,

(Mrs.) Dr. Lakshmy

Convenor

Co-Convenor

Member-Secretary

Members

Joglekar, S.G.

Kumar, Manoj

Bhowmick, Alok

Chandke, A.S.

Gupta, Vinay

Garg,Dr S.K.

Huda, Y.S.

Pandey, Alok

Puri, S.K.

Mukherjee, M.K.

Roy, Samit Chaudhuri

Saha, Dr. G.P.

Sharma, Aditya

Sharan, G.

Subbarao, Dr. H.

Sarangi, D.

Srivastava, O.P.

Thakkar, Dr. S.K.

Thandavan, K.B.

Viswanathan, T.

Verma, G.L.

CE (B) S&R, MORTH(A.RPathak)

Corresponding Members

Bhattacharya, Dr. S.K.

Jain, Dr. S.K.

Kanhere, D.K.

Heggade, V.N.

Rao, Dr. M.V.B.

Ex-officio Members

Kandasamy, C.

Prasad, Vishnu Shankar

Director General (Road Development)

& Special Secretary, MoRT&H and

President, IRC

Secretary General, Indian Roads Congress

2

SCOPE

IRC:6-2014

The object of the Standard Specifications and Code of Practice is to establish a common

procedure for the design and construction of road bridges in India. This publication is meant

to serve as a guide to both the design engineer and the construction engineer but compliance

with the rules therein does not relieve them in any way of their responsibility for the stability

and soundness of the structure designed and erected by them. The design and construction

of road bridges require an extensive and through knowledge of the science and technique

involved and should be entrusted only to specially qualified engineers with adequate practical

experience in bridge engineering and capable of ensuring careful execution of work.

201 CLASSIFICATION

201.1 Road bridges and culverts shall be divided into classes according to the loadings

they are designed to carry.

IRC Class 70R Loading: This loading is to be normally adopted on all roads on which

permanent bridges and culverts are constructed. Bridges designed for Class 70R Loading

should be checked for Class A Loading also as under certain conditions, heavier stresses

may occur under Class A Loading.

IRC Class AA Loading: This loading is to be adopted within certain municipal limits, in certain

existing or contemplated industrial areas, in other specified areas, and along certain specified

highways. Bridges designed for Class AA Loading should be checked for Class A Loading

also, as under certain conditions, heavier stresses may occur under Class A Loading.

IRC Class A Loading: This loading is to be normally adopted on all roads on which permanent

bridges and culverts are constructed.

IRC Class B Loading: This loading is to be normally adopted for timber bridges.

For particulars of the above four types of loading, see Clause 204.

201.2 Existing bridges which were not originally constructed or later strengthened to take

one of the above specified I.R.C. Loadings will be classified by giving each a number equal

to that of the highest standard load class whose effects it can safely withstand.

Annex A gives the essential data regarding the limiting loads in each bridge's class, and

forms the basis for the classification of bridges.

201.3 Individual bridges and culverts designed to take electric tramways or other special

loadings and not constructed to take any of the loadings described in Clause 201.1 shall be

classified in the appropriate load class indicated in Clause 201.2.

3

IRC:6-2014

202 LOADS, FORCES AND STRESSES

202.1 The loads, forces and stresses to be considered in designing road bridges and

culverts are :

1) Dead Load G

2) Live Load Q

3) Snow Load

(see note i)

4) Impact factor on vehicular live load Q.^

5) Impact due to floating bodies or

vessels as the case may be F

6) Vehicle collision load

7) Wind load W8) Water current F

9) Longitudinal forces caused by tractive

effort of vehicles or by braking of vehicles

and/or those caused by restraint of movement

of free bearings by friction or deformation F/F/F^

10) Centrifugal force F^^

11) Buoyancy G^

12) Earth pressure including live load

surcharge, if any F^^

13) Temperature effects F^^

(see note ii)

14) Deformation effects F^

15) Secondary effects F^

16) Erection effects F' e

17) Seismic force F

er

eq

18) Wave pressure F

(see note iii)

19) Grade effect G(see note iv)

wp

e

4

IRC:6-2014

Notes

:

i) The snow loads may be based be based on actual observation or past records in the

particular area or local practices, if existing.

ii) Temperature effects (F^^) in this context is not the frictional force due to the movement

of bearing but forces that are caused by the restraint effects.

iii) The wave forces shall be determined by suitable analysis considering drawing

and inertia forces etc. on single structural members based on rational methods or

model studies. In case of group of piles, piers etc., proximity effects shall also be

considered.

iv) For bridges built in grade or cross-fall, the bearings shall normally be set level by varying

the thickness of the plate situated between the upper face of the bearing and lower

^ face of the beam or by any other suitable arrangement. However, where the bearings

are required to be set parallel to the inclined grade or cross-fall of the superstructure,

an allowance shall be made for the longitudinal and transverse components of the

vertical loads on the bearings.

202.2.2 All mennbers shall be designed to sustain safely most critical combination of various

loads, forces and stresses that can co-exist and all calculations shall tabulate distinctly

the various combinations of the above loads and stresses covered by the design. Besides

temperature, effect of environment on durability shall be considered as per relevant codes.

202.3 Combination of Loads and Forces and Permissible Increase in Stresses

The load combination shown in Table 1 shall be adopted for working out stresses in the

members. The permissible increase of stresses in various members due to these combinations

are also indicated therein. These combinations of forces are not applicable for working out

base pressure on foundations for which provision made in relevant IRC Bridge Code shall be

adopted. For calculating stresses in members using working stress method of design the load

combination shown in Table 1 shall be adopted.

The load combination as shown in Annex B shall be adopted for limit state design

approach.

203 DEAD LOAD

The dead load carried by a girder or member shall consist of the portion of the weight of the

superstructure (and the fixed loads carried thereon) which is supported wholly or in part by

the girder or member including its own weight. The following unit weights of materials shall be

used in determining loads, unless the unit weights have been determined by actual weighing

of representative samples of the materials in question, in which case the actual weights as

thus determined shall be used.

5

IRC:6-201 4

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!RC:6-2014

2) Any load combination involving temperature, wind and/or earthquake acting

independently or in combination, maximum permissible tensile stress in Prestressed

Concrete Members shall be limited to the value as per relevant Code (IRC:112).

3) Use of fractional live load shown in Table 1 is applicable only when the design live load

given in Table 2 is considered. The structure must also be checked with no live load.

4) The gradient effect due to temperature is considered in the load combinations MB and

I MB. The reduced live load (Q) is indicated as 0.5. Its effects (F^, F^, and FJ are also

shown as 0.5, as 0.5 stands for the reduced live load to be considered in this case.

However for F^ it is shown as 1 , since it has effects of dead load besides reduced live

load. Q.^ being a factor of live load as shown as 1 . Whenever a fraction of live load 0.5

shown in the above Table under column Q is specified, the associated effects due to

live load {Q.^, F^, F^, Fând FJ shall be considered corresponding to the associated

fraction of live load. When the gradient effect is considered, the effects, if any, due to

overall rise or fall of temperature of the structure shall also be considered.

5) Seismic effect during erection stage is reduced to half in load combination IX when

construction phase does not exceed 5 years.

6) The load combinations (VIII and IX) relate to the construction stage of a new bridge. For

repair, rehabilitation and retrofitting, the load combination shall be project-specific.

7) Clause 219.5.2 may be referred to, for reduction of live load in Load Combination Vl.

Materials Weight

(t/m3)

1) Ashlar (granite) 2.7

2) Ashlar (sandstone) 2.4

3) Stone setts :

a) Granite 2.6

b) Basalt - 2.7

4) Ballast (stone screened, broken, 2.5 cm to 7.5 cm

guage, loose):

a) Granite 1.4

b) Basalt 1.6

5) Brickwork (pressed) in cement mortar 2.2

6) Brickwork (common) in cement mortar 1.9

7) Brickwork (common) in lime mortar 1.8

7

IRC:6-2014

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28) Steel (rolled or cast) 7.8

204 LIVE LOADS

204.1 Details of I.R.C. Loadings

204.1.1 For bridges classified under Clause 201.1, the design live load shall consist of

standard wheeled or tracked vehicles or trains of vehicles as illustrated in Figs. 1 to 3 andAnnex A. The trailers attached to the driving unit are not to be considered as detachable.

204.1.2 Within the kerb to kerb width of the roadway, the standard vehicle or train shall be

assumed to travel parallel to the length of the bridge and to occupy any position which will

produce maximum stresses provided that the minimum clearances between a vehicle andthe roadway face of kerb and between two passing or crossing vehicles, shown in Figs. 1 to

3, are not encroached upon.

204.1.3 For each standard vehicle or train, all the axles of a unit of vehicles shall be

considered as acting simultaneously in a position causing maximum stresses.

8

IRC:6-2014

12t

0)$

1 2t 17t I7t I7t

K.'Ot II

i

.0.61 3.960 1.520 2.130j

1.370I

3.050 1.370 0.91

CLASS 70R (WHEELED) - LONGITUDINAL POSITION

20t

MAX. SINGLE

AXLE LOAD

20t 20t

W.'v<.'<X<CTO'V.'<^VX'<x'V.'<,A'<XVU

I1.850 i 1.220 , 1.830

|

MAX. BOGIE LOAD

MMIMUM TYRE PRESSURE 2

0.41

2.790

0.862.790

0.41 0.38 i

r

n

2.790

10.51 0..25 0.23

C.[D.DnDnna.SA. 0.41x0.61BA. 0.41x0.61

•L' TYPE

SA. 0.41x0.61BA. 0.41x0.61

'M' TYPE

SA. 0.23x0.51BA. 0.23x0.51

•N' TYPE

MINIMUM WHEEL SPACING & TYRE SIZE OF CRIT ICAL (HEAVIEST) AXLE

WHEEL ARRANGEMENT FOR TOR (WHEELED VEHICLE)

4.570 90.000 (MIN.)I

4.570

CLASS 70R (TRACK) - LONG ITUD INAL POSITION

CLASS 70R (T)

35t 35t

0.84 0.84

2.900

Notes

WHEEL ARRANGEMENT FOR 70R (TRACKED) VEHICLE

Fig. 1 Class 70R Tracked and Wheeled Vehicles (Clause 204.1)

1 ) The nose to tail spacing between two successive vehicles shall not be less than 90 mfor tracked vehicle and 30 m for wheeled vehicle.

2) For multi-lane bridges and culverts, each Class 70R loading shall be considered

to occupy two lanes and no other vehicle shall be allowed in these two lanes. The

passing/crossing vehicle can only be allowed on lanes other than these two lanes.

Load combination is as shown in Table 2.

3) The maximum loads for the wheeled vehicle shall be 20 tonne for a single axle or

40 tonne for a bogie of two axles spaced not more than 1 .22 m centres.

9

Class 70R loading is applicable only for bridges having carriageway width of 5.3 m and

above (i.e. 1.2 x 2 + 2.9 = 5.3). The minimum clearance between the road face of the

kerb and the outer edge of the wheel or track, 'C, shall be 1 .2 m.

The minimum clearance between the outer edge of wheel or track of passing or

crossing vehicles for multilane bridge shall be 1 .2 m. Vehicles passing or crossing can

be either same class or different class, Tracked or Wheeled.

Axle load in tonnes, linear dimension in meters.

For tyre tread width deductions and other important notes, refer NOTES given in

Annex A.

18 500

Min.

1.800

SECTION ON P-P

1.800

f-

4-

-f

if'i

;

O I

Ifl. J

A?

i-

PLANDRIVING VEHICLE

8.300 1.200 4.800 1-200 4.8OO 18.500

Iff t f

2.7 2.7 11.4 11.4 6.8 6.8 6.8 6.8

Class A Train of Vehicles

Fig. 2 Class 'A' Train of Vehicles (Clause 204. 1

)

10

IRC:6-2014

The nose to tail distance between successive trains sliall not be less than 18.5 m.

For single lane bridges having carriageway width less than 5.3 m, one lane of Class Ashall be considered to occupy 2.3 m. Remaining width of carriageway shall be loaded

with 500 Kg/m^, as shown in Table 2.

For multi-lane bridges each Class A loading shall be considered to occupy single lane

for design purpose. Live load combinations as shown in Table 2 shall be followed.

The ground contact area of the wheels shall be as under:

Axle load (tonne) Ground contact area

B (mm) W (mm)

11.4 250 500

6.5 200 380

2.7 150 200

CLEAR CARRIAGEWAY WIDTH

WW WW1. 5) The mininnum clearance, / between outer edge of the wheel and the

roadway face of the kerb and the minimum clearance, g, between the outer

edges of passing or crossing vehicles on multi-lane bridges shall be as given

below:-

Clear carriageway width g f5.3 m(*)to 6.1 m(**) Varying between 0.4 m to 1 .2 m 150 mm for all carriageway width

Above 6.1 m 1.2m

(*) = [2x(1.8+0.5)+0.4+2x0.15]

(**)= [2x(1.8+0.5)+1.2+2x0.15]

6) Axle loads in tonne. Linear dimensions in metre.

Notes :

1)

2)

3)

4)

11

IRC;6-2014

1.800

SECTION ON P-P

"Wt* ^5

—

1 ill-1

-!

^!

CO

]

PLANDRIVING VEHICLE

18.500

Mm.

"

8.300 l.-ZOO 4.800 1-200 4300 .18.500

Notes :

Class B Train of Vehicles

Fig. 3 Class 'B' Train of Vehicles (Clause 204.1

)

1) The nose to tail distance between successive trains shall not be less than

18.5 m.

12

IRC:6-2014

No other live load shall cover any part of the carriageway when a train of vehicles

(or trains of vehicles in multi-lane bridge) is crossing the bridge.

The ground contact area of the wheels shall be as under:-

Axle load (tonne) Ground contact area

B (mm) W(mm)

6.8 200 380

4.1 150 300

1.6 125 175

CLEAR CARRIAGEWAY WIDTH

WW WWFor bridges having carriageway width less than 5.06 m, only single lane of Class B

loading shall be considered.

The minimum clearances, / between outer edge of the wheel and the roadway face

of the kerb and the minimum clearance, g, between the outer edges of passing or

crossing vehicles on multi-lane bridges shall be as given below:

Axle loads in tonne. Linear dimensions in metre.

Clear carriageway width 9 /

5.06 m(*) to 5.86 m(**)

Above 5.86 m

Varying between 0.4 m to

1.2 m

1.2 m

1 50 mm for all carriageway

widths

n = [2x(1. 8+0. 38) +0.4+2x0. 1 5]

(**)=[2x(1.8+0.38)+1. 2+2x0. 1 5]

13

IRC:6-2014

204.1.4 Vehicles in adjacent lanes shall be taken as headed in the direction producing

maximum stresses.

204.1 .5 The spaces on the carriageway left uncovered by the standard train of vehicles shall

not be assumed as subject to any additional live load unless otherwise shown in Table 2.

204.2 Dispersion of Load through Fills of Arch Bridges

The dispersion of loads through the fills above the arch shall be assumed at 45 degrees both

along and perpendicular to the span in the case of arch bridges.

204.3 Combination of Live Load

This clause shall be read in conjunction with Clause 112.1 of IRC:5.The carriageway live load

combination shall be considered for the design as shown in Table 2.

Table 2 Live Load Combination

SI.

No.

Carriageway Width

(CW)Number of Lanes for

Design PurposesLoad Combination

1) Less than 5.3 1 One lane of Class A considered to

occupy 2.3 m. The remaining width

of carriageway shall be loaded with

500 kg/m2

2) 5.3 m and above but less

than 9.6 m2 One lane of Class 70R OR two lanes

for Class A

3) 9.6 m and above but less

than 13.1

3 One lane of Class 70R for every two

lanes with one lanes of Class A on the

remaining lane OR 3 lanes of Class A

4) 13.1 m and above but

less than 16.6 m4

One lane of Class 70R for every two

lanes with one lane of Class A for the

remaining lanes, if any, OR one lane of

Class A for each lane.


less than 20.1

5


less than 23.6

6

Notes

:

1 ) The minimum width of the two-lane carriageway shall be 7.5 m as per Clause 112.1 of

IRC:5.

2) See Note No. 2 below Fig. 1A of Annex A regarding use of 70R loading in place of

Class AA Loading and vice-versa.

14

IRC:6-2014

Table 2 Live Load Combinations

S.NO. NO. OF LANESFOR DESIGNPURPOSE

CARRIAGEWAY WIDTH (CW) & LOADING ARRANGEMENT

4.25m < CW < 5.3m

1 LANECLASS A

I 1.8

0.15MO(MIN.)

CASE 1 : CLASS A - 1 LANE

5.3m < CW < 9.6m

2 LANESCU\SS 70R(W)

(MIN.)

CASE 1 : CLASS TOR (W)

CLASS A

5.3m < CW < 9.6m

(MIN.)

CLASS A

0.15

(mInT)'

CASE 2: CLASS A - 2 LANES

3 LANES9.6m < CW < 13.1m

(MIN.)

CASE 1 : CLASS A - 3 LANES

9.7m « CW < 13.1m

CLASS A

1.2 (MIN.)

CLASS 70R{W)

0.15|'O|

(MIN.) 7.25

1

(MIN.)

(NO OTHER VEHICLE PERMITTEDIN THIS ZONE)

CASE 2 : CLASS A - 1 LANE + CLASS 70R (W)

15

IRC:6-2014

Table 2 : Live Load Combinations contd..

S.NO NO. OF LANESFOR DESIGNPURPOSE


4 LANES 13.1m ^: CW < 16.6m

CLASS A

1 .2

(MIN.)

CLASS A

(MIN.)

CLASS A

(MIN.)

CLASS A

0.15l[d|

(MIN.)


13.2m ^: CW < 16.6m

Hi

CLASS A

1 .2

(MIN.

CLASS A

1.2 (MIN.)

CLASS 70R(W)

0.15,|o|

(MIN.) 7.25 (MIN.)

CASE 2 ; CLASS A - 2 LANE +CLASS 70R (W)


CLASS 70R(W)

14.5m ^ CV/ < 16.6m

1.2 (MIN.)

CLASS 70R(W)

I1-2

I

:(MIN.)114

7.25 7.25 (MIN.)



CASE 3 : CLASS 70R (W) - 2 LANES

5 LANES

16.6m CW < 20. 1r

(MIN.)


16.7m CW < 20.1m

i ..,1:2.

7.25 (W"^-

(NO OTHER' VEHICLE PERMITTEDIN THIS ZONE)

CASE 2 : CLASS A - 3 LANES +CLASS 70R (W)

16

IRC:6-2014

Table 2 Live Load Coi ins Contd.,



5 LANESCONTD...

16.8m < CVJ < 20.1m

CU\SS 70R(W)

.2 (MIN.)

CLASS A

1.8I

1.2 (MIN.)

CLASS 70R(W)

I 1.2, I'^l

\'".\I

1.2,

(MIN.)7 25 . m 12^ -,

25(MIN.)



CASE 3 : CLASS 70R (W) - 2 LANES + CLASS A -1 LANE

16.7m ^ CW < 20.1m

1.2 (MIN.)

CLfliSS 70R(W)

1.2 (MIN.)

CLASS 70R{W)

(MIN.) 7.0 7.25 (MIN.



CASE 4 ; CLASS A -1 LANE + CLASS 70R (W) - 2 LANES

6 LANES 20.1m CW < 23.6m

(MIN.)


20.2m « CW < 23.6m

CLASS A

0.1 5l o[

1.2

(MIN.)'

CLASS A

1.2

(MIN.)

CLASS A

1 .2

(MiN.y

CLASS A

1.2 (MIN.)

CLASS 70R(W)

1 .2

(MIN.) 7.25 (MIN.)

CASE 2 ; CLASS A - 4 LANES + CLASS 70R (W)(NO OTHER VEHICLE PERMITTED

IN THIS ZONE)

17

IRC:6-2014

Table 2 Live Load Combinations Contd.



6 LANESCONTD...

20.2m « CW < 23.6m

1.2 (MIN.)

CLASS 70R(W)

1.2 (MIN.)

CLASS 70R(W)

(MIN.) 7.0 7.25 (MIN.)


CASE 3 : CLASS A - 2- LANES + CLASS 70R (W) - 2 LANES

20.3m ^; CW < 23.5m

CU\SS 70R(W)

1.2 (MIN.)

CLASS A

1.2

(MIN.)

CLASS A

1.2 (MIN.

CL^SS 70R(W)

i 1.2.

7.25(NO OTHER VEHICLE PERMITTED

IN THIS ZONE)

7.25 (MIN.)


CASE 4 : CLASS 70R (W) + CLASS A - 2 LANES + CLASS 70R (W)

Notes :

1 ) Class 70R Wheeled loading in the Table 2 can be replaced by Class 70R tracked, Class

AA tracked or Class AA wheeled vehicle.

2) Maximum number of vehicles which can be considered, are only shown in the Table 2. In

case minimum number of vehicles govern the design (e.g. torsion) the same shall also be

considered.

3) All dimensions in Table 2 are in metre.

204.4 Congestion Factor

For bridges, flyovers/grade seperators close to areas such as ports, heavy industries and

nriines and any other areas where frequent congestion of heavy vehicles may occur, additional

check for congestion of vehicular live load on the carriageway shall be considered. In the

absence of any stipulated value, the congestion factor, as mentioned in Table 3 shall be

considered. This factor shall be used as a multiplying factor on the global effect of vehicular

live load only. Under this condition, horizontal force due to braking/acceleration, centrifugal

action and temperature gradient effect need not be included, but the effect of live load impact

shall be included.

18

IRC:6-2014

Table 3

ol. NO. B_Jopan Kan96 uongssiion racior

T) MDOVG lU 111 dllU UpiO OU ill 1 . 1 o

2) 30.0 m to 40.0 m 1.15to 1.30

3) 40.0 m to 50.0 m 1.30 to 1.45

4) 50.0 m to 60.0 m 1.45 to 1.60

5) 60.0 m to 70.0 m 1.60 to 1.70

6) Beyond 70.0 m 1.70

Note : For Intermediate bridges spans, the value of multiplying factor may be interpolated.

205 REDUCTION IN THE LONGITUDINAL EFFECT ONBRIDGES ACCOMMODATING MORE THAN

TWO TRAFFIC LANES

Reduction in the longitudinal effect on bridges having more than two traffic lanes due to the

low probability that all lanes will be subjected to the characteristic loads simultaneously shall

be in accordance with the Table shown below:

Number of lanes Reduction in longitudinal effect

For two lanes No reduction

For three lanes 10% reduction

For four lanes 20% reduction

For five or more lanes 20% reduction

Notes:

1 ) However, it should be ensured that the reduced longitudinal effects are not less severe

than the longitudinal effect, resulting from simultaneous loads on two adjacent lanes.

Longitudinal effects mentioned above are bending moment, shear force and torsion in

longitudinal direction.

2) The above Table is applicable for individually supported superstructure of multi-laned

carriageway. In the case of separate sub-structure and foundations, the number of lanes

supported by each of them is to be considered while working out the reduction percentage.

In the case of combined sub-structure and foundations, the total number of lanes for both

the carriageway is to be considered while working out the reduction percentage.

206 FOOT OVER BRIDGE, FOOTWAY, KERB, RAILINGS,PARAPET AND CRASH BARRIERS

The horizontal force specified for footway, kerb, railings, parapet and crash barriers in this

section need not be considered for the design of main structural members of the bridge.

However, the connection between kerb/railings/papapet, crash barrier and the deck should

be adequately designed and detailed.

19

IRC:6-2014

206.1 For all parts of bridge floors accessible only to pedestrians and animals and for

all footways the loading shall be 400 kg/m^. For the design of foot over bridges the loading

shall be taken as 500 kg/m^. Where crowd loads are likely to occur, such as, on bridges

located near towns, which are either centres of pilgrimage or where large congregational fairs

are held seasonally, the intensity of footway loading shall be increased from 400 kg/m^ to

500 kg/m^. When crowd load is considered, the bridge should also be designed for the case

of entire carriageway being occupied by crowd load.

206.2 Kerbs, 0.6 m or more in width, shall be designed for the above loads and for a local

lateral force of 750 kg per metre, applied horizontally at top of the kerb. If kerb width is less

than 0.6 m, no live load shall be applied in addition to the lateral load specified above.

206.3 In bridges designed for any of the loadings described in Clause 204.1, the main

girders, trusses, arches, or other members supporting the footways shall be designed for the

following live loads per square metre for footway area, the loaded length of footway taken in

each case being, such as, to produce the worst effects on the member under consideration:

a) For effective span of 7.5 m or less, 400 kg/m^ or 500 kg/m^ as the case may be,

based on Sub-Clause 206.1.

b) For effective spans of over 7.5 m but not exceeding 30 m, the intensity of load

shall be determined according to the equation :

P = pi_ M0L-3Q09 J

c) For effective spans of over 30 m, the intensity of load shall be determined

according to the equation :

4800^ M6.5-W^P = P^-260 +

where,15 J

= 400 kg/m^ or 500 kg/m^ as the case may be, based on Sub-Clause 206.1 .When

crowd load is considered for design of the bridge, the reduction mentioned in

this clause will not be applicable.

P = the live load in kg/m^ -

'

L = the effective span of the main girder, truss or arch in m, and

W = width of the footway in m

206.4 Each part of the footway shall be capable of carrying a wheel load of 4 tonne, which

shall be deemed to include impact, distributed over a contact area 300 mm in diameter; the

permissible working stresses shall be increased by 25 percent to meet this provision. This

provision need not be made where vehicles cannot mount the footway as in the case of a

footway separated from the roadway by means of an insurmountable obstacle, such as, truss

or a main girder.

Note ; A footway kerb shall be considered mountable by vehicles.

20

IRC:6-2014

206.5 The Pedestrian/Bicycle Railings/Parapets

The pedestrian/bicycle railings/parapets can be of a large variety of construction. The design

loads for two basic types are given below:-

i) Type: Solid/partially filled in parapet continuously cantilevering along full length from

deck level.

Loading: Horizontal and vertical load of 150 kg/m acting simultaneously on the top level

of the parapet.

ii) Type: Frame type with discrete vertical posts cantilevering from the curb/deck with

minimum two rows of horizontal rails (third row bring the curb itself, or curb

replaced by a low level 3'"^ rail). The rails may be simply supported or continuous

over the posts.

Loading: Each horizontal railing designed for horizontal and vertical load of 150 kg/m,

acting simultaneously over the rail. The filler portion, supported between any

two horizontal rails and vertical rails should be designed to resist horizontal load

of 150 kg/m^. The posts to resist horizontal load of 150 kg/m X spacing between

posts in metres acting on top of the post.

206.6 Crash Barriers

Crash barriers are designed to withstand the impact of vehicles of certain weights at certain

angle while travelling at the specified speed. They are expected to guide the vehicle back

on the road while keeping the level of damage to vehicle as well as to the barriers within

acceptable limits.

Following are the three categories for different applications:

Category Application ContaDnment for

P-1: Normal Containment Bridges carrying expressway, or

equivalent

15 kN vehicle at 110 km/h, and20° angle of impact

P-2: Low Containment All other bridges except bridge

over railways

15 kN vehicle at 80 km/h and20° angle of impact

P-3: High Containment At hazardous and high risk

locations, over busy railway lines,

complex interchanges, etc.

300 kN vehicle at 60 km/h and20° angle of impact

The barriers can be of rigid type, using cast-in-situ/precast reinforced concrete panels, or of

flexible type, constructed using metallic cold-rolled and/or hot-rolled sections. The metallic

type, called semi-rigid type, suffer large dynamic deflection of the order of 0.9 to 1 .2 m impact,

whereas the 'rigid' concrete type suffer comparatively negligible deflection. The efficacy of

the two types of barriers is established on the basis of full size tests carried out by the

laboratories specializing in such testing. Due to the complexities of the structural action, the

value of impact force cannot be quantified.

21

IRC:6-2014

A certificate from such laboratory can be the only basis of acceptance of the semi-rigid type,

in which case all the design details and construction details tested by the laboratory are to be

followed in toto without modifications and without changing relative strengths and positions

of any of the connections and elements.

For the rigid type of barrier, the same method is acceptable. However, in absence of testing/test

certificate, the minimum design resistance shown in Table 4 should be built into the section.

Table 4 Minimum Design Resistance

SLNo.

Requirement Types of Crash Barrier

P-1 In-situ/

Precast

P-2 In-situ/

Precast

P-3 In-situ

1) Shape Shape on traffic side to be as per IRC:5, or NewJersey (NJ) Type of 'F' Shape designated thus

by AASHTOMinimum graoe ot concreie M40 M40 M40

3) Minimum thickness of R C wall

( at top)

175 mm 175 mm 250 mm

4) Minimum moment of resistance

at base of the wall [see note (i)]

for bending in vertical plane with

reinforcement adjacent to the

traffic face [see note (ii)]

15 kNm/m 7.5 kNm/m 100 kNm/m for

end section and

75 kNm/m for

intermediate section

[see note (iii)]


for bending in horizontal plane

with reinforcement adjacent to

outer face [see note (ii)]

7.5 kNm/m 3.75 kNm/m 40 kNm/m


of anchorage at the base of a

precast reinforced concrete

panel

22.5

kNm/m11.25

kNm/mNot applicable

7) Minimum transverse shear

resistance at vertical joints

between precast panels, or at

vertical joints made between

lengths of in-situ crash barrier.

44 kN/m of

joint

22.5 kN/mof joint

Not applicable

8) Minimum height 900 mm 900 mm 1550 mm

Notes :

i) The base of wall refers to horizontal sections of the parapet within 300 mm above the

adjoining paved surface level. The minimum moments of resistance shall reduce linearly

from the base of wall value to zero at top of the parapet.

ii) In addition to the main reinforcement, in items 4 & 5 above, distribution steel equal to

50 percent of the main reinforcement shall be provided in the respective faces.

22

IRC:6-2014

iii) For design purpose the crash barrier Type P-3 shall be divided into end sections extending

a distance not greater than 3.0 m from ends of the crash barrier and intermediate sections

extending along remainder of the crash barrier.

iv) If concrete barrier is used as a median divider, the steel is required to be placed on both

sides.

v) In case of P-3 In-situ type, a minimum horizontal transverse shear resistance of 1 35 kN/m

shall be provided.

206.7 Vehicle Barriers/Pedestrian Railing between Footpath and Carriageway

Where considerable pedestrian traffic is expected, such as, in/near townships, rigid type of

reinforced concrete crash barrier should be provided separating the vehicular traffic fronn the

same. The design and construction details should be as per Clause 206.6. For any other type

of rigid barrier, the strength should be equivalent to that of rigid RCC type.

For areas of low intensity of pedestrian traffic, semi-rigid type of barrier, which suffers large

deflections can be adopted.

207 TRAMWAY LOADING

207.1 When a road bridge carries tram lines, the live load due to the type of tram cars

sketched in Fig. 4 shall be computed and shall be considered to occupy a 3 m width of

roadway.

207.2 A nose to tail sequence of the tram cars or any other sequence which produces the

heaviest stresses shall be considered in the design.

^5.500 ;:,>'

t.(

OC1

i

j 1

—

r

j

j

„.1L.". _ i L

,1

1 _..

SINGLE TRUCK (SINGLE DECK)

3.200

JJI.M.30!)—

'

-6.140 6.140-

t.l

BOOESCAR (SINGLE DECK)

1

4900

LI ill

—1

^, 20

Fig. 4 Average Dimension of Tramway Rolling Stock (Clause 207.1)

23

IRC:6-2014

Notes :

1) Clearance between passing single deck bogie cars on straight tracks laid at

standard 2.75 m track centres shall be 300 mm.

2) Clearance between passing double bogie cars on straight tracks laid at standard

2.75 m track centres shall be 450 mm.

3) Linear dimensions in metre.

ROLLING STOCK WEIGHT

Description Loaded Weight (Tonne) Unloaded Weight (Tonne)

Single truck (Single deck) 9.6 7.9

Bogie car (Single deck) 15.3 12.2

Bogie car (Double deck) 21.5 16.0

207.3 Stresses shall be calculated for the following two conditions and the maximumthereof considered in the design:-

a) Tram loading, followed and preceded by the appropriate standard loading

specified in Clause 204.1 together with that standard loading on the traffic lanes

not occupied by the tram car lines.

b) The appropriate standard loading specified in Clause 204.1 without any tram cars.

208 IMPACT

208.1 Provision for impact or dynamic action shall be made by an increment of the live load by

an impact allowance expressed as a fraction or a percentage of the applied live load.

208.2 For Class A or Class B Loading

In the members of any bridge designed either for Class A or Class B loading (vide Clause

204.1), this impact percentage shall be determined from the curves indicated in Fig. 5. The

impact fraction shall be determined from the following equations which are applicable for

spans between 3 m and 45 m.

i) Impact factor fraction for 4^reinforced concrete bridges

ii) Impact factor fraction for steel bridges

6 + L

9

13.5 + /.

Where L is length in metres of the span as specified in Clause 208.5

24

IRC:6-2014

208.3 For Class AA Loading and Class TOR Loading

The value of the impact percentage shall be taken as follows:-

a) For spans less than 9 m :

1 ) for tracked vehicles

208.4

b)

2) for wheeled vehicles

For spans of 9 m or more :

i) Reinforced concrete bridges

1) Tracked vehicles

2) ^heeled vehicles

25 percent for spans upto 5 m linearly

reducing to 1 0 percent for spans upto 9 m

25 percent

10 percent upto a span of 40 m andin accordance with the curve in Fig. 5

for spans in excess of 40 m.

25 percent for spans upto 12 m and

in accordance with the curve in Fig. 5

for spans in excess of 12 m.

ii) Steel bridges

3) Tracked vehicles

4) Wheeled vehicles

10 percent for all spans

: 25 percent for spans upto 23 m and in

accordance with the curve indicated

in Fig. 5 for spans in excess of 23 m.

No impact allowance shall be added to the footway loading specified in Clause 206.

12 15 18 21 24 27 30 33 36 39

Span in Metre

42 45 48 51 54 57

Fig. 5 Impact Percentage for Highway Bridges for Class A and Class B Loading (Clause 208.2)

25

IRC:6-2014

208.5 The span length to be considered for arriving at the impact percentages specified in

Clause 208.2 and 208.3 shall be as follows:

a) For spans simply supported or continuous or for arches

the effective span on which the load is placed.

b) For bridges having cantilever arms without suspended spans

the effective overhang of the cantilever arms reduced by 25 percent for loads

on the cantilever arms and the effective span between supports for loads on

the main span.

c) For bridges having cantilever arms with suspended span

the effective overhang of the cantilever arm plus half the length of the

suspended span for loads on the cantilever arm, the effective length of the

suspended span for loads on the suspended span and the effective span

between supports for load on the main span.

Note : For individual members of a bridge, such as, a cross girder or deck slab, etc. the value of

L mentioned in Clause 208.2 or the spans mentioned in clause 208.3 shall be the effective

span of the member under consideration.

208.6 In any bridge structure where there is a filling of not less than 0.6 m including the

road crust, the impact percentage to be allowed in the design shall be assumed to be one-

half of what is specified in Clauses 208.2 and 208.3.

208.7 For calculating the pressure on the bearings and on the top surface of the bed

blocks, full value of the appropriate impact percentage shall be allowed. But, for the design

of piers abutments and structures, generally below the level of the top of the bed block, the

appropriate impact percentage shall be multiplied by the factor given below:

a) For calculating the pressure at the

bottom surface of the bed block .... 0.5

b) For calculating the pressure on the .... 0.5

top 3 m of the structure below the bed block decreasing

uniformly to zero

c) For calculating the pressure on the portion of the zero

structure more than 3 m below the bed block

26

IRC:6-2014

208.8 In the design of members subjected to among other stresses, direct tension, such

as, hangers in a bowstring girder bridge and in the design of member subjected to direct

compression, such as, spandrel columns or walls in an open spandrel arch, the impact

percentage shall be taken the same as that applicable to the design of the corresponding

member or members of the floor system which transfer loads to the tensile or compressive

members in question.

208.9 These clauses on impact do not apply to the design of suspension bridges and foot

over bridges. In cable suspended bridges and in other bridges where live load to dead load

ratio is high, the dynamic effects such as vibration and fatigue shall be considered. For long

span foot over bridges (with frequency less than 5 Hz and 1.5 Hz in vertical and horizontal

direction) the dynamic effects shall be considered, if necessary, for which specialist literature

may be referred.

209 WIND LOAD

209.1 This clause is applicable to normal span bridges with individual span length up to

150 m or for bridges with height of pier up to 100 m. For all other bridges including cable

stayed bridges, suspension bridges and ribbon bridges specialist literature shall be used for

computation of design wind load.

209.1.1 The wind pressure acting on a bridge depends on the geographical locations,

the terrain of surrounding area, the fetch of terrain upwind of the site location, the local

topography, the height of bridge above the ground, horizontal dimensions and cross-section

of bridge or its element under consideration. The maximum pressure is due to gusts that

cause local and transient fluctuations about the mean wind pressure.

All structures shall be designed for the wind forces as specified in Clause 209.3 and 209.4.

These forces shall be considered to act in such a direction that the resultant stresses in the

member under consideration are maximum.

In addition to applying the prescribed loads in the design of bridge elements, stability against

overturning, uplift and sliding due to wind shall be considered.

209.2 The wind speed at the location of bridge shall be based on basic wind speed map as

shown in Fig. 6. The intensity of wind force shall be based on hourly mean wind speed and

pressure as shown in Table 5. The hourly mean wind speed and pressure values given in

Table 5 corresponds to a basic wind speed of 33 m/s, return period of 100 years, for bridges

situated in plain terrain and terrain with obstructions, with a flat topography. The hourly mean

wind pressure shall be appropriately modified depending on the location of bridge for other

27

IRC:6-2014

basic wind speed as shown in Fig. 6 and used for design (see notes below Table 5).

Table 5 Hourly Mean Wind Speed And Wind Pressure

(For a basic wind speed of 33 m/s as shown in Fig. 6)

Brid ge Situated in

Plain Terrain Terrain with Obstructions

(m/s) (N/m2)

Up to 10 m 27.80 463.70 17.80 190.50

15 29.20 512.50 19.60 230.50on 30.30 550.60 21.00 265.30

30 31.40 590.20 22.80 312.20

50 33.10 659.20 24.90 373.40

60 33.60 1 676.30 25.60 392.90

70 34.00 693.60 26.20 412.80

80 34.40 711.20 26.90 433.30

90 34.90 729.00 27.50 454.20

100 35.30 747.00 28.20 475.60

H = the average height in metres of exposed surface above the mean retarding surface

(ground or bed or water level)

= hourly mean speed of wind in m/s at height H

P = horizontal wind pressure in N/m^ at height H

Notes :

1 ) Intermediate values may be obtained by linear interpolation.

2) Plain terrain refers to open terrain with no obstruction or with very well scattered

obstructions having height up to 10 m. Terrain with obstructions refers to a terrain with

numerous closely spaced structures, forests or trees upto 10 m in height with few

isolated tall structures or terrain with large number of high closed spaced obstruction

like structures, trees forests etc.

3) For other values of basic wind speed as indicated in Fig. 6, the hourly mean wind

speed shall be obtained by multiplying the corresponding wind speed value by the

ratio of basic wind speed at the location of bridge to the value corresponding to

Table 5, (i.e., 33 m/sec.) ^

4) The hourly mean wind pressure at an appropriate height and terrain shall be obtained by

multiplying the corresponding pressure value for base wind speed as indicated in Table 5

by the ratio of square of basic wind speed at the location of wind to square of base wind

speed corresponding to Table 5 (i.e., 33 m/sec).

5) If the topography (hill, ridge escarpment or cliff) at the structure site can cause

acceleration or tunneling of wind, the wind pressure shall be further increased by

20 percent as stated in Note 4.

6) For construction stages, the hourly mean wind pressure shall be taken as 70 percent

of the value calculated as stated in Note 4 and 5.

7) For the design of foot over bridges in the urban situations and in plain terrain, a minimumhorizontal wind load of 1.5 kN/m^ (150 kg/m^) and 2 kN/m^ (200 kg/m^) respectively

shall be considered to be acting on the frontal area of the bridge.

28

INTENSITY OF WIND PRESSURE IRC:6-2014

84 88 92 96

28

24

20

16.

12

Jalsalmer

Patiala Qehradû",,""'""^Bathinda Saharanpur

Karnal AlmoraHisar

chi.i, Meerut

.

Rohtakogiî

FaridabadJhunjhunun

Rampur

Barellly

Sikar

NagaurJaipur

Alwar Bahraich

Agra

Barmer

Jodhpur

Pali

Ajmer

Gwalior

Bundi Shivpur

Sirohi Kota

Udalpur

r%^^ P^''"P"^ Mandsahr

MahesanaBhuj GandhinagarSurendranaga Ahmadabad

Vadodara

havnagar

Sural Jalgaon

Dhule

Silvassa

Nasik

Miyibai

LucknowGon I

Surendranaga

Jammoar ^

Gorakhpur

Raebareî Muzaffarpur

Allahabad Patna

Nawada

Dumka ^garti

Dhanbad

RanchiBhopal

Jabalpur Ambikapur

Oispur

Hamirpur

Jhansi

GunaP*"""

"isorh sagar

Vararâsi

AurangabadRewa

Indore

\kola

AurangabadAdilabad

Ahmadnagar

Pune

Osrnanabad

Solapur

Seoni

BetuI

'^"9P"^ Bandara RaipuAmravathi

Yavatmalor I

Chandrapur

Nanded Jagdalpur

Karlmnagar

Bidar Warangal

Hyderabad

Bllespur

Jamshedpur^^|^^,^

Raurkela "«<^*5jPW

uhargahKsenduu

aambalj^^MkShulaba^^^V

Kurnool

lellary

Bangalora

M)aor« Dharmapurl

Wr Salei

Colmbatore

Trichut' Tiruchrapalll^

Madurai

Cochin Raineswarm

Korapi

Vishakhapatn

555047443933

Quilon

Thiruvanathapuram

Kanniyakumarl

Tutlcorin

24

20

16

12

72 76 80 84 88 92

Fig. 6 Wind Map of India (Source: IS: 875 (Part-3)-1987)

29

iRC:6-2014

209.3 Design Wind Force on Superstructure

209.3.1 The superstructure shall be designed for wind induced horizontal forces (acting

in the transverse and longitudinal direction) and vertical loads acting simultaneously. Theassumed wind direction shall be perpendicular to longitudinal axis for a straight structure or

to an axis chosen to maximize the wind induced effects for a structure curved in plan.

209.3.2 The transverse wind force on a bridge superstructure shall be estimated as specified

in Clause 209.3.3 and acting on the area calculated as follows:

a) For a deck structure:

The area of the structure as seen in elevation including the floor system and

railing, less area of perforations in hand railing or parapet walls shall be

considered. For open and solid parapets, crash barriers and railings, the solid

area in normal projected elevation of the element shall be considered.

b) For truss structures:

Appropriate area as specified in Annex C shall be taken.

c) For construction stages

The area at all stages of construction shall be the appropriate unshielded solid

area of structure.

209.3.3 The transverse wind force (in N) shall be taken as acting at the centroids of the

appropriate areas and horizontally and shall be estimated from: ^

F^ = P^xA^xGxC^

where, is the hourly mean wind pressure in N/m^ (see Table 5), is the solid area in m^

(see Clause 209.3.2), G is the gust factor and is the drag coefficient depending on the

geometric shape of bridge deck.

For highway bridges up to a span of 150 m, which are generally not sensitive to dynamic

action of wind, gust factor shall be taken as 2.0.

The drag coefficient for slab bridges with width to depth ratio of cross-section, i.e b/d > 10

shall be taken as 1.1.

For bridge decks supported by single beam or box girder, C,^ shall be taken as 1.5 for b/d

ratio of 2 and as 1.3 if b/d > 6. For intermediate b/d ratios C^ shall be interpolated. For deck

supported by two or more beams or box girders, where the ratio of clear distance between

the beams of boxes to the depth does not exceed 7, C^ for the combined structure shall be

taken as 1 .5 times C^ for the single beam or box.

For deck supported by single plate girder it shall be taken as 2.2. When the deck is supported

by two or more plate girders, for the combined structure C^ shall be taken as 2(1 +c/20cy), but

not more than 4, where c is the centre to centre distance of adjacent girders, and d is the

depth of windward girder.

For truss girder superstructure the drag coefficients shall be derived as given in Annex C.

For other type of deck cross-sections shall be ascertained either from wind tunnel tests or,

if available, for similar type of structure, specialist literature shall be referred to.

31

IRC:6-2014

209.3.4 The longitudinal force on bridge superstructure (in N) shall be taken as 25 percent

and 50 percent of the transverse wind load as calculated as per Clause 209.3.3 for beam/box/plate girder bridges and truss girder bridges respectively.

209.3.5 An upward or downward vertical wind load (in N) acting at the centroid of the

appropriate areas, for all superstructures shall be derived from:

F^= P^xA^xGxC^

where

is the hourly mean wind pressure in N/m^ at height H (see Table 5)

is the area in plan in m^

is the lift coefficient which shall be taken as 0.75 for normal type of slab, box,

l-girder and plate girder bridges. For other type of deck cross-sections shall

be ascertained either from wind tunnel tests or, if available, for similar type of

structure. Specialist literature shall be referred to.

G is the gust factor as defined in 209.3.3

209.3.6. The transverse wind load per unit exposed frontal area of the live load shall be

computed using the expression given in Clause 209.3.3 except that against shall

be taken as 1 .2. The exposed frontal area of live load shall be the entire length of the

superstructure seen in elevation in the direction of wind as defined in clause or any part of

that length producing critical response, multiplied by a height of 3.0 m above the road waysurface. Areas below the top of a solid barrier shall be neglected.

The longitudinal wind load on live load shall be taken as 25 percent of transverse wind load

as calculated above. Both loads shall be applied simultaneously acting at 1.5 m above the

roadway.

209.3.7 The bridges shall not be considered to be carrying any live load when the wind

speed at deck level exceeds 36 m/s.

209.3.8 In case of cantilever construction an upward wind pressure of P^ x C^x G N/m^ (see

Clause 209.3.5 for notations) on bottom soffit area shall be assumed on stabilizing cantilever

arm in addition to the transverse wind effect calculated as per Clause 209.3.3. In addition to

the above, other loads defined in Clause 218.3 shall also be taken into consideration.

209.4 Design Wind Forces on Substructure

The substructure shall be designed for wind induced loads transmitted to it from the

superstructure and wind loads acting directly on the substructure. Loads for wind directions

both normal and skewed to the longitudinal centerline of the superstructure shall be

considered.

F^ shall be computed using expression in Clause 209.3.3 with taken as the solid area in

normal projected elevation of each pier. No allowance shall be made for shielding.

For piers, shall be taken from Table 6. For piers with cross-section dissimilar to those

given in Table 5, C shall be ascertained either from wind tunnel tests or, if available, for

32

IRC:6-2014

similar type of structure, specialist literature shall be referred to shall be derived for each

pier, without shielding.

Table 6 Drag Coefficients For Piers

PLAN SHAPE

t

b

HEIGHTFOR PIER RATIOS OF

BREADTH

1 2 4 6 10 20 40

\A/iMnVVIINU

b1<-~4

1.3 1.4 1.5 1.6 1.7 1 .9 2.1

1

3

1

2

1.3 1.4 1.5 1.6 1.8 2.0 2.2

2

31.3 1.4 1.5 1.6 1.8 2.0 2.2

1 1.2 1.3 1.4 1.5 1.6 1.8 2.0

21.0 1.1 1.2 1.3 1.4 1.5 1.7

2 0.8 0.9 1.0 1.1 1.2 1.3 1.4

1

3 0.8 0.8 0.8

0.8

0.9 0.9 1.0 1.2

>4 0.8 0.8 0.9 0.9 0.9 1.1b

SQUAREOROCTAGONAL \

1.0 1.1 1.2 1.3 1.4 1.4 1.4

12 SIDE POLYGON

0.7 0.8 0.9 0.9 1.0 1.1 1.3

0.6

d

CIRCLE WITH SMOOTHSURFACE HEREf > 6 mV S

0.5 0.5 0.5 0.5 0.5 0.6

d<

CIRCLE WITH SMOOTHSURFACE WHEREf V > 6 mV SCIRCLE WITH ROUGHSURFACE OR WITHPROJECTIONS

0.7 0.7 0.8 0.8 0.9 1.0 1.2

33

IRC:6-2014

Notes :

1) For rectangular piers with rounded corners with radius r, the value of derived from

Table 6 shall be multiplied by (1-1 .5 r/b) or 0.5, whichever is greater.

2) For a pier with triangular nosing, shall be derived as for the rectangle encompassing

the outer edges of pier.

3) For pier tapering with height, shall be derived for each of the unit heights into

which the support has been subdivided. Mean values of t and b for each unit height

shall be used to evaluate t/b. The overall pier height and mean breadth of each unit

height shall be used to evaluate height/breadth.

4) After construction of the superstructure shall be derived for height to breadth

ratio of 40.

209.5 Wind Tunnel Testing

Wind tunnel testing by established procedures shall be conducted for dynamically

sensitive structures such as cable stayed, suspension bridges etc., including modeling of

appurtenances.

210 HORIZONTAL FORCES DUE TO WATER CURRENTS

210.1 Any part of a road bridge which may be submerged in running water shall be

designed to sustain safely the horizontal pressure due to the force of the current.

210.2 On piers parallel to the direction of the water current, the intensity of pressure shall

be calculated from the following equation:

P = 52K\/

where,

P = intensity of pressure due to water current, in kg/m^

V = the velocity of the current at the point where the pressure intensity is being

calculated, in metre per second, and

K = a constant having the following values for different shapes of piers illustrated

in Fig. 7

i) Square ended piers (and for the superstructure) 1.50

ii) Circular piers or piers with semi-circular ends 0.66

iii) Piers with triangular cut and ease waters, the angle

included between the faces being 30° or less 0.50

34

IRC:6-2014

iv) Piers with triangular cut and ease waters, the angle

included between the faces being more than 30°

but less than 60°

v) -do- 60 to 90°

vi) Piers with cut and ease waters of equilateral

arcs of circles

vii) Piers with arcs of the cut and ease waters

intersecting at 90°

Piers with square ends

0.50 to 0.70

0.70 to 0.90

0.45

0.50

Circular piers or piers with semi-

circular ends

Piers with triangular cut and easewaters, the angle included betweenthe faces being 30 degrees or less

80°

Piers with triangular cut and easewaters, the angle included betweenthe faces being more than 30degrees but less than 60 degrees

Piers with triangular cut and easewaters, the angle included betweenthe faces being 60 to 90 degrees

Piers with cut and ease waters of

equilateral arcs of circles

Piers with arcs of the cut and easewaters intersecting at 90 degrees

Fig. 7 Shapes of Bridge Piers (Clause 210.2)

35

IRC:6-2014

210.3 The value of in the equation given in Clause 210.2 shall be assumed to vary

linearly from zero at the point of deepest scour to the square of the maximum velocity at

the free surface of water. The maximum velocity for the purpose of this sub-clause shall be

assumed to be V2 times the maximum mean velocity of the current.

Square of velocity at a height X from the point of deepest Scour = =

where

V is the maximum mean velocity.

210.4 When the current strikes the pier at an angle, the velocity of the current shall be

resolved into two components - one parallel and the other normal to the pier.

a) The pressure parallel to the pier shall be determined as indicated in

Clause 21 0.2 taking the velocity as the component of the velocity of the current

in a direction parallel to the pier.

b) The pressure of the current, normal to the pier and acting on the area of the

side elevation of the pier, shall be calculated similarly taking the velocity as the

component of the velocity of the current in a direction normal to the pier, and the

constant K as 1.5, except in the case of circular piers where the constant shall

be taken as 0.66

210.5 To provide against possible variation of the direction of the current from the direction

assumed in the design, allowance shall be made in the design of piers for an extra variation in

the current direction of 20 degrees that is to say, piers intended to be parallel to the direction

of current shall be designed for a variation of 20 degrees from the normal direction of current

and piers originally intended to be inclined at 6 degree to the direction of the current shall be

designed for a current direction inclined at (20±e) degrees to the length of the pier.

210.6 In case of a bridge having a pucca floor or having an inerodible bed, the effect of

cross-currents shall in no case be taken as less than that of a static force due to a difference

of head of 250 mm between the opposite faces of a pier.

210.7 When supports are made with two or more piles or trestle columns, spaced closer

than three times the width of piles/columns across the direction of flow, the group shall be

POINT OF DEEPEST SCOUR

Free surface of water

— 2

36

IRC:6-2014

treated as a solid rectangle of the same overall length and width and the value of K taken

as 1.25 for calculating pressures due to water currents, both parallel and normal to the

pier. If such piles/columns are braced, then the group should be considered as a solid pier,

irrespective of the spacing of the columns.

211 LONGITUDINAL FORCES

211.1 In all road bridges, provision shall be made for longitudinal forces arising from any

one or more of the following causes:

a) Tractive effort caused through acceleration of the driving wheels;

b) Braking effect resulting from the application of the brakes to braked wheels;

and

c) Frictional resistance offered to the movement of free bearings due to change of

temperature or any other cause.

NOTE . Braking effect is invariably greater than the tractive effort.

211.2 The braking effect on a simply supported span or a continuous unit of spans or on

any other type of bridge unit shall be assumed to have the following value:

a) In the case of a single lane or a two lane bridge : twenty percent of the first

train load plus ten percent of the load of the succeeding trains or part thereof,

the train loads in one lane only being considered for the purpose of this sub-

clause. Where the entire first train is not on the full span, the braking force

shall be taken as equal to twenty percent of the loads actually on the span or

continuous unit of spans.

b) In the case of bridges having more than two-lanes: as in (a) above for the

first two lanes plus five per cent of the loads on the lanes in excess of two.

Note : The loads in this Clause shall not be increased on account of impact.

211.3 The force due to braking effect shall be assumed to act along a line parallel to the

roadway and 1 .2 m above it. While transferring the force to the bearings, the change in the

vertical reaction at the bearings should be taken into account.

211 .4 The distribution of longitudinal horizontal forces among bridge supports is effected by

the horizontal deformation of bridges, flexing of the supports and rotation of the foundations.

For spans resting on stiff supports, the distribution may be assumed as given below in

Clause 211.5. For spans resting on flexible supports, distribution of horizontal forces may be

carried out according to procedure given below in Clause 211.6.

211.5 Simply Supported and Continuous Spans on Unyielding Supports

211 .5.1 Simply supported spans on unyielding supports

211.5. 1. 1 For a simply supported span with fixed and free bearings (other than elastomeric

type) on stiff supports, horizontal forces at the bearing level in the longitudinal direction shall

37

IRC:6-2014

be greater of the two values given below:

Fixed bearing Free bearing

or pii) -^^MiR^^RJ ^(f^.^f^J

where,

= Applied Horizontal force

R = Reaction at the free end due to dead load9

R = Reaction at free end due to live loadq

|j= Coefficient of friction at the movable bearing which shall be assumed to have the

following values:

i) For steel roller bearings 0.03

ii) For concrete roller bearings 0.05

iii) For sliding bearings:

a) Steel on cast iron or steel on steel 0.4

b) Gray cast iron

Gray cast iron (Mechanite) 0.3

c) Concrete over concrete with bitumen

layer in between 0.5

d) Teflon on stainless steel 0.03 and 0.05

whichever is governing

Note

:

a) For design of bearings, the corresponding forces may be taken as per relevant IRC

Codes.

b) Unbalanced dead load shall be accounted for properly. The structure under the fixed

bearing shall be designed to withstand the full seismic and design braking/tractive force.

211.5.1.2 In case of simply supported small spans upto 10 m resting on unyielding

supports and where no bearings are provided, horizontal force in the longitudinal direction at

the bearing level shall be

-5l or pR^ whichever is greater

211.5.1.3 For a simply supported span siting on identical elastomeric bearings at each

end resting on unyielding supports. Force at each end

V = shear rating of the elastomer bearings

= movement of deck above bearing, other than that due to applied forces

38

IRC:6-2014

211.5. 1.4 The substructure and foundation shall also be designed for 1 0 percent variation

in movement of the span on either side.

211.5.2 For continuous bridges with one fixed bearing or other free bearings:

Fixed bearing Free bearing

Case-I

(|jR - |jL) +ve acting in +ve direction

(a) If, F,>2mR

F^-(IjR + |jL)

(b) lf,F^<2|jR

|jRx

Case-ll

(jjR - |jL) +ve F^ acting in -ve direction

(a) if,F,>2|jL

F,-(mR + mL)

(b) if,F,<2ML

'^h +(|jR-|jL)

whichever is greater

|jRx

where,

n^ or n,^ = number of free bearings to the left or right of fixed bearings, respectively

|jL or pR = the total horizontal force developed at the free bearings to the left or right

of the fixed bearing respectively

pR^ = the net horizontal force developed at any one of the free bearings

considered to the left or right of the fixed bearings

Note : In seismic areas, the fixed bearing shall also be checked for full seismic force and braking/

tractive force. The structure under the fixed bearing shall be designed to withstand the full

seismic and design braking/tractive force.

211.6 Simply Supported and Continuous Spans on Flexible Supports

211 .6.1 Shear rating of a support is the horizontal force required to move the top of the support

through a unit distance taking into account horizontal deformation of the bridges, flexibility of

the support and rotation of the foundation. The distribution of 'applied' longitudinal horizontal

forces (e.g., braking, seismic, wind etc.) depends solely on shear ratings of the supports and

may be estimated in proportion to the ratio of individual shear ratings of a support to the sumof the shear ratings of all the supports.

39

IRC:6-2014

211.6.2 The distribution of self-induced horizontal force caused by deck movement (owing

to temperature, shrinkage, creep, elastic shortening, etc.) depends not only on shear ratings

of the supports but also on the location of the 'zero' movement point in the deck. The shear

rating of the supports, the distribution of applied and self-induced horizontal force and the

determination of the point of zero movement may be made as per recognized theory for

which reference may be made to publications on the subjects.

211.7 The effects of braking force on bridge structures without bearings, such as, arches,

rigid frames, etc., shall be calculated in accordance with approved methods of analysis of

indeterminate structures.

211.8 The effects of the longitudinal forces and all other horizontal forces should be

calculated upto a level where the resultant passive earth resistance of the soil below the

deepest scour level (floor level in case of a bridge having pucca floor) balances these

forces.

212 CENTRIFUGAL FORCES

212.1 Where a road bridge is situated on a curve, all portions of the structure affected by

the centrifugal action of moving vehicles are to be proportioned to carry safely the stress

induced by this action in addition to all other stress to which they may be subjected.

212.2 The centrifugal force shall be determined from the following equation:

127R

where,

C = Centrifugal force acting normally to the traffic (1) at the point of action of the

wheel loads or (2) uniformly distributed over every metre length on which a

uniformly distributed load acts, in tonnes.

W = Live load (1) in case of wheel loads, each wheel load being considered as

acting over the ground contact length specified in Clause 204, in tonnes, and

(2) in case of a uniformly distributed live load, in tonnes per linear metre.

V - The design speed of the vehicles using the bridge in km per hour, and

R - The radius of curvature in metres.

212.3 The centrifugal force shall be considered to act at a height of 1 .2 m above the level

of the carriageway.

212.4 No increase for impact effect shall be made on the stress due to centrifugal action.

40

IRC:6-2014

212.5 The overturning effect of the centrifugal force on the structure as a whole shall also

be duly considered.

213 BUOYANCY

213.1 In the design of abutments, especially those of submersible bridges, the effects of

buoyancy shall also be considered assuming that the fill behind the abutments has been

removed by scour.

213.2 To allow for full buoyancy, a reduction shall be made in the gross weight of the

member affected by reducing its density by the density of the displaced water.

Note: 1 )The density of water may be taken as 1 .0 t/m^

2) For artesian condition, HFL or actual water head, whichever is higher, shall be

considered for calculating the uplift.

213.3 In the design of submerged masonry or concrete structures, the buoyancy effect

through pore pressure may be limited to 15 percent of full buoyancy.

213.4 In case of submersible bridges, the full buoyancy effect on the superstructure shall

be taken into consideration.

214 EARTH PRESSURE

214.1 Structures designed to retain earth fills shall be proportioned to withstand pressure

calculated in accordance with any rational theory. Coulomb's theory shall be acceptable,

subject to the modification that the centre of pressure exerted by the backfill, when considered

dry, is located at an elevation of 0.42 of the height of the wall above the base instead of 0.33

of that height. No structures shall, however, be designed to withstand a horizontal pressure

less than that exerted by a fluid weighing 480 kg/m^ All abutments and return walls shall be

designed for a live load surcharge equivalent to 1 .2 m earth fill.

214.2 Reinforced concrete approach slab with 12 mm dia 150 mm c/c in each direction

both at top and bottom as reinforcement in M30 grade concrete covering the entire width of

the roadway, with one end resting on the structure designed to retain earth and extending for

a length of not less than 3.5 m into the approach shall be provided.

214.3 All designs shall provide for the thorough drainage of backfilling materials by meansof weep holes and crushed rock or gravel drains, or pipe drains, or perforated drains.

214.4 The pressure of submerged soils (not provided with drainage arrangements) shall

be considered as made up of two components:

a) Pressure due to the earth calculated in accordance with the method laid down

in Clause 214.1 , the unit weight of earth being reduced for buoyancy, and

b) Full hydrostatic pressure of water

41

IRC:6-2014

215 TEMPERATURE

215.1 General

Daily and seasonal fluctuations in shade air temperature, solar radiation, etc. cause the

following:

a) Changes in the overall temperature of the bridge, referred to as the effective

bridge temperature. Over a prescribed period there will be a minimum and a

maximum, together with a range of effective bridge temperature, resulting in

loads and/or load effects within the bridge due to:

1) Restraint offered to the associated expansion/contraction by the form

of construction (e.g., portal frame, arch, flexible pier, elastomeric

bearings) referred to as temperature restraint; and

ii) Friction at roller or sliding bearings referred to as frictional bearing

restraint;

b) Differences in temperature between the top surface and other levels through the

depth of the superstructure, referred to as temperature difference and resulting

in associated loads and/or load effects within the structure.

Provisions shall be made for stresses or movements resulting from variations in the

temperature.

215.2 Range of Effective Bridge Temperature

Effective bridge temperature for the location of the bridge shall be estimated from the

isotherms of shade air temperature given on Figs. 8 and 9. Minimum and maximum effective

bridge temperatures would be lesser or more respectively than the corresponding minimum

and maximum shade air temperatures in concrete bridges. In determining load effects due

to temperature restraint in concrete bridges the effective bridge temperature when the

structure is effectively restrained shall be taken as datum in calculating the expansion up to

the maximum effective bridge temperature and contraction down to the minimum effective

bridge temperature.

42

IRC:6-2014

68 72 76 80 84 88 92 96

68 72 76 80 ,34 88 92

The territorial waters of India extend into the sea to a distance of twelve nautical miles measured from the

appropriate base line.

Based upon Survey of India map with permission of the Surveyor General of India.

© Government of India Copyright 1993

Responsibility for the correctness of internal details rests with the publishers.

Fig. 8 Chart Showing Highest Maximum Temperature

43

IRC:6-2014

68 72 76 80 84 88 92 98

68 72 76 80 84 88 92

The territorial waters of India extend into the sea to a distance of twelve nautical miles measured from theappropriate base line.

Based upon Survey of India map with permission of the Surveyor General of India

© Government of India copyright 1993.

Responsibility for the correctness of internal details rests with the publishers.

Fig. 9 Chart Showing Lowest Minimum Temperature

44

IRC:6-2014

The bridge temperature when the structure is effectively restrained shall be estimated as

follows:

Bridge location having difference between

maximum and minimum air shade temperature

Bridge temperature to be assumed when the

structure is effectively restrained

>20°C Mean of maximum and minimum air shade

temperature ± 10°C whichever is critical

< 20°C Mean of maximum and minimum air shade

temperature ± 5°C whichever is critical

For metallic structures the extreme range of effective bridge temperature to be considered in

the design shall be as follows :

1) Snowbound areas from - 35°C to + 50°C

2) For other areas (Maximum air shade temperature + 15°C) to (minimum air shade

temperature - 10°C). Air shade temperatures are to be obtained from Figs. 8 and 9.

215.3 Temperature Differences

Effect of temperature difference within the superstructure shall be derived from positive

temperature differences which occur when conditions are such that solar radiation and other

effects cause a gain in heat through the top surface of the superstructure. Conversely, reverse

temperature differences are such that heat is lost from the top surface of the bridge deck as

a result of re-radiation and other effects. Positive and reverse temperature differences for

the purpose of design of concrete bridge decks shall be assumed as shown in Fig. 10 (a).

These design provisions are applicable to concrete bridge decks with about 50 mm wearing

surface. So far as steel and composite decks are concerned, Fig. 10 (b) may be referred for

assessing the effect of temperature gradient.

Positive Temperature Differences

17.8°

Reverse Temperature Differences

10.6°

^2

J

h, = 0.3h < 0,15 m

= 0.3h > 0.10 m

h = h = 0.2h < 0.25 m

iij = = 0.25h < 0.25 m

< 0.25 m

Ii3 = 0.3h< 0.15 m

Fig. 10 (a) Design Temperature Differences for Concrete Bridge Decks

45

IRC:6-2014

50 mm surfacing 50 mm surfacing 50 mm surfacing

Xh

h, = 0.6h

hj = 0.4m

H(m) IT, CO0^2 18

03 20.5

8

h (m)I

T, CO0.2 4.4

0.3 6.8

Fig. 10 (b) Temperature Differences Across Steel and Composite Section

Note : For intermediate slab thickness, may be interpolated.

215.4 Material Properties

For the purpose of calculating temperature effects, the coefficient of thermal expansion for

RCC, PSC and steel structures may be taken as 12.0 x 10 Vc.

215.5 Permissible Increase in Stresses and Load Combinations

Tensile stresses resulting from temperature effects not exceeding in the value of two third of

the modulus of rupture may be permitted in prestressed concrete bridges. Sufficient amount

of non-tensioned steel shall, however, be provided to control the thermal cracking. Increase

in stresses shall be allowed for calculating load effects due to temperature restraint under

load combinations.

Note : Permissible increase in stresses and load combinations as stated under Clause 215.5 is

not applicable for Limit State Design of Bridges.

216.1 A deformation stress is defined as the bending stress in any member of an open

web-girder caused by the vertical deflection of the girder combined with the rigidity of the

joints.

216.2 All steel bridges shall be designed, manufactured and erected in a manner such

that the deformation stresses are reduced to a minimum. In the absence of calculation,

deformation stresses shall be assumed to be not less than 16 percent of the dead and live

loads stresses.

216.3 In prestressed girders of steel, deformation stresses may be ignored.

216 DEFORMATION STRESSES (for steel bridges only)

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217 SECONDARY STRESSES

217.1 a) Steel structures: Secondary stresses are additional stresses brought into play

due to the eccentricity of connections, floor beam loads applied at intermediate

points in a panel, cross girders being connected away from panel points, lateral

wind loads on the end-posts of through girders etc., and stresses due to the

movement of supports.

b) Reinforced Concrete structures: Secondary stresses are additional stresses

brought into play due either to the movement of supports or to the deformations

in the geometrical shape of the structure or its member, resulting from causes,

such as, rigidity of end connection or loads applied at intermediate points of

trusses or restrictive shrinkage of concrete floor beams.

217.2. All bridges shall be designated and constructed in a manner such that the secondary

stresses are reduced to a minimum and they shall be allowed for in the design.

217.3 For reinforced concrete members, the shrinkage coefficient for purposes of design

may be taken as 2 X 10 ^.

218 ERECTION STRESSES AND CONSTRUCTION LOADS218.1 The effects of erection as per actual loads based on the construction programmeshall be accounted for in the design. This shall also include the condition of one span being

completed in all respects and the adjacent span not in position. However, one span dislodged

condition need not be considered in the case of slab bridge not provided with bearings.

218.2 Construction loads are those which are incident upon a structure or any of its

constituent components during the construction of the structures.

A detailed construction procedure associated with a method statement shall be drawn up

during design and considered in the design to ensure that all aspects of stability and strength

of the structure are satisfied.

218.3 Examples of Typical Construction Loadings are given below. However, each

individual case shall be investigated in complete detail.

Examples:

a) Loads of plant and equipment including the weight handled that might be

incident on the structure during construction.

b) Temporary super-imposed loading caused by storage of construction material

on a partially completed a bridge deck.

c) Unbalanced effect of a temporary structure, if any, and unbalanced effect

of modules that may be required for cantilever segmental construction of a

bridge.

d) Loading on individual beams and/or completed deck system due to travelling of

a launching truss over such beams/deck system.

e) Thermal effects during construction due to temporary restraints.

f) Secondary effects, if any, emanating from the system and procedure of

construction.

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g) Loading due to any anticipated soil settlement.

h) Wind load during construction as per Clause 209. For special effects, such

as, unequal gust load and for special type of construction, such as, long span

bridges specialist literature may be referred to.

i) Seismic effects on partially constructed structure as per Clause 219.

219 SEISMIC FORCE219.1 Applicability

219.1.1 All bridges supported on piers, pier bents and arches, directly or through bearings,

and not exempted below in the category (a) and (b), are to be designed for horizontal and

vertical forces as given in the following clauses.

The following types of bridges need not be checked for seismic effects:

a) Culverts and minor bridges up to 10 m span in all seismic zones

b) Bridges in seismic zones II and ill satisfying both limits of total length not

exceeding 60 m and spans not exceeding 15 m

219.1.2 Special investigations should be carried out for the bridges of following description:

a) Bridges more than 150 m span

b) Bridges with piers taller than 30 m in Zones IV and V

c) Cable supported bridges, such as extradosed, cable stayed and suspension

bridges

d) Arch bridges having more than 50 m span

e) Bridges having any of the special seismic resistant features such as seismic

isolators, dampers etc.

f) Bridges using innovative structural arrangements and materials.

Notes for special investigations:

1) In all seismic zones, areas covered within 10 km from the known active faults

are classified as 'Near Field Regions'. For all bridges located within 'Near Field

Regions', except those exempted in Clause 219.1.1, special investigations

should be carried out. The information about the active faults should be sought

by bridge authorities for projects situated within 100 km of known epicenters as

a part of preliminary investigations at the project preparation stage.

2) Special investigations should include aspects such as need for site specific

spectra, independency of component motions, spatial variation of excitation,

need to include soil-structure interaction, suitable methods of structural analysis

in view of geometrical and structural non-linear effects, characteristics and

reliability of seismic isolation and other special seismic resistant devices, etc.

3) Site specific spectrum, wherever its need is established in the special

investigation, shall be used, subject to the minimum values specified for relevant

seismic zones, given in Fig. 11.

48

Fig. 11 Seismic Zones of India (IS 1893 (Part l):2002)

NOTE: Bridge locations and towns falling at the boundary line demarcating two zones shall

be considered in the higher zone.

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219.1.3 Masonry and plain concrete arch bridges with span more than 10 m shall be avoided

in Zones IV and V and in 'Near Field Region'.

219.2 Seismic Zones

For the purpose of determining the seismic forces, the Country is classified into four zones

as shown in Fig. 11. For each Zone a factor 'Z' is associated, the value of which is given in

Table 7.

Table 7 Zone Factor (Z)

Zone No. Zone Factor

(Z)

V 0.36

IV 0.24

III 0.16

II 0.10

219.3 Components of Seismic Motion

The characteristics of seismic ground motion expected at any location depend upon the

magnitude of earthquake, depth of focus, distance of epicenter and characteristics of the path

through which the seismic wave travels. The random ground motion can be resolved in three

mutually perpendicular directions. The components are considered to act simultaneously, but

independently and their method of combination is described in Clause 219.4. Two horizontal

components are taken as of equal magnitude, and vertical component is taken as two third

of horizontal component.

In zones IV and V the effects of vertical components shall be considered for all elements of

the bridge.

The effect of vertical component may be omitted for all elements in zones II and III, except

for the following cases:

a) prestressed concrete decks

b) bearings and linkages

c) horizontal cantilever structural elements

d) for stability checks and

e) bridges located in the 'Near Field Regions'

219.4 Combination of Component Motions

1) The seismic forces shall be assumed to come from any horizontal direction.

For this purpose two separate analyses shall be performed for design seismic

forces acting along two orthogonal horizontal directions. The design seismic

force resultants (i.e. axial force, bending moments, shear forces, and torsion)

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IRC:6-2014

at any cross-section of a bridge component resulting from the analyses in the

two orthogonal horizontal directions shall be combined as below (Fig. 12).

a) ±r^±0.3r2

b) ±0.3r^±r2 ^

where,

r^= Force resultant due to full design seismic force along x direction.

r^= Force resultant due to full design seismic force along z direction.

2) When vertical seismic forces are also considered, the design seismic force resultants

at any cross section of a bridge component shall be combined as below:

a) ±r^±0.3r2±0.3r3

b) ± 0.3 r^± rî 0.3r3

c) ± 0.3r^± 0.3 r^t r3

where r^ and are as defined above and r3 is the force resultant due to full design seismic

force along the vertical direction.

X

Fig. 12 Combination of Orthogonal Seismic Forces

Moments for Ground Motion

along X-axis

Moments for Ground Motion

along Z-axis

Design Moments

M- =m5 +0.3M?

= 0.3Mf + Mf M„ = 0.3 + M?

Where, M and M are absolute moments about local axes.' X z

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Note : Analysis of bridge as a wliole is carried out for global axes X and Z and effects obtained are

combined for design about local axes as shown.

219.5 Computation of Seismic Response

Following methods are used for computation of seismic response depending upon the

complexity of the structure and the input ground motion.

1) For most of the bridges, elastic seismic acceleration method is adequate.

In this method, the first fundamental mode of vibration is calculated and the

corresponding acceleration is read from Fig. 13. This acceleration is applied to

all parts of the bridge for calculation of forces as per Clause 219.5.1

2) Elastic Response Spectrum Method: This is a general method, suitable for

more complex structural systems (e. g. continuous bridges, bridges with large

difference in pier heights, bridges which are curved in plan, etc), in which

dynamic analysis of the structure is performed to obtain the first as well as

higher modes of vibration and the forces obtained for each mode by use of

response spectrum from Fig. 13 and Clause 219.5.1. These modal forces are

combined by following appropriate combinational rules to arrive at the design

^ forces. Reference is made to specialist literature for the same.

3.0

2.5

2.0

1.5

1-0

as

0.0 0.6 1-0 T.5 2.0 2.5 3.0 3.5 4.0

Fig. 13 Response Spectra

Note : For structural components like short and rigid abutments, the value of Sjq shall be

taken as 1. Also, the response reduction factor R shall be taken as 1.0 for seismic

design of such structures.

219.5.1 Horizontal seismic force

The horizontal seismic forces acting at the centers of mass, which are to be resisted by the

structure as a whole, shall be computed as follows:

Fg =\ (Dead Load + Appropriate Live Load)

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where,

F = seismic force to be resistedeq

A^= horizontal seismic coefficient = (Z/2) x (I) x (S^/g)

Appropriate live load shall be taken as per Clause 219.5.2

Z = Zone factor as given in Table 7

I= Importance Factor (see Clause 219.5.1.1)

T = Fundamental period of the bridge (in sec.) for horizontal vibrations

Fundamental time period of the bridge member is to be calculated by any rational

method of analysis adopting the Modulus of Elasticity of Concrete (E^^) as per

IRC:112, and considering moment of inertia of cracked section which can be taken

as 0.75 times the moment of inertia of gross uncracked section, in the absence of

rigorous calculation. The fundamental period of vibration can also be calculated by

method given in Annex D.

SJg = Average response acceleration coefficient for 5 percent damping of load

resisting elements depending upon the fundamental period of vibration T as given

in Fig. 13 which is based on the following equations.

For rocky or hard soil sites, Type I soil with N > 30

S3J

2.50 1 0.0 < 7 < 0.40

y[i.oo/rJ o.40<r<4.oo

For medium soil sites. Type II soil with 10 < N < 30

S3J

2.50 1 0.0 <7<0.55

y|l.36/7j 0.55<7<4.00

For soft soil sites, Type III soil with N < 10

S3 j 2.50 1 0.0 < 7 < 0.67

y|l.67/7j 0.67<7<4.00

Note : In the absence of calculations of fundamental period for small bridges, the value of SJgmay be taken as 2.5.

For damping other than 5 percent offered by load resisting elements, the multiplying factors

as given below shall be used.

Damping % 2 5 10

Factor 1.4 1.0 0.8

Application Prestressed concrete,

Steel and composite steel

elements

Reinforced Concrete

elements

Retrofitting of

old bridges with RC piers

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219.5.1.1 Seismic importance factor (I)

Bridges are designed to resist design basis earthquake (DBE) level, or other higher or

lower magnitude of forces, depending on the consequences of their partial or complete

non-availability, due to damage or failure from seismic events. The level of design force

is obtained by multiplying (Z/2) by factor T, which represents seismic importance of the

structure. Combination of factors considered in assessing the consequences of failure and

hence choice of factor T,- include inter alia,

a) Extent of disturbance to traffic and possibility of providing temporary diversion,

b) Availability of alternative routes,

c) Cost of repairs and time involved, which depend on the extent of damages, -

minor or major,

d) Cost of replacement, and time involved in reconstruction in case of failure,

e) Indirect economic loss due to its partial or full non-availability, Importance factors

are given in Table 8 for different types of bridges.

Table 8 Importance Factor

Seismic Class Illustrative Examples Importance Factor '1'

Normal bridges All bridges except those mentioned in

other classes

1

Important bridges a) River bridges and flyovers inside cities

b) Bridges on National and State

Highways

c) Bridges sen/ing traffic near ports and

other centers of economic activities

d) Bridges crossing railway lines

1.2

Large critical bridges in all

Seismic Zonesa) Long bridges more than 1km length

across perennial rivers and creeks

b) Bridges for which alternative routes are

not available

1.5

Note : While checking for seismic effects during construction, the importance factor of 1 should be

considered for all bridges in all zones.

219.5.2 Live load components

1) The seismic force due to live load shall not be considered when acting in the

direction of traffic, but shall be considered in the direction perpendicular to the

traffic.

ii) The horizontal seismic force in the direction perpendicular to the traffic shall be

calculated using 20 percent of live load (excluding impact factor).

iii) The vertical seismic force shall be calculated using 20 percent of live load

(excluding impact factor).

Note : The reduced percentages of live loads are applicable only for calculating the magnitude of

seismic design force and are based on the assumption that only 20 percent of the live load

is present over the bridge at the time of earthquake.

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219.5.3 Water current and depth of scour

The depth of scour under seismic condition to be considered for design shall be 0.9 times the

maximum scour depth. The flood level for calculating hydrodynamic force and water current

force is to be taken as average of yearly maximum design floods. For river bridges, average

may preferably be based on consecutive 7 years' data, or on local enquiry in the absence of

such data.

219.5.4 Hydrodynamic and earth pressure forces under seismic condition

In addition to inertial forces arising from the dead load and live load, hydrodynamic forces

act on the submerged part of the structure and are transmitted to the foundations. Also,

additional earth pressures due to earthquake act on the retaining portions of abutments. For

values of these loads reference is made to IS 1893. These forces shall be considered in the

design of bridges in zones IV and V.

The modified earth pressure forces described in the preceding paragraph need not be

considered on the portion of the structure below scour level and on other components, such

as wing walls and return walls.

219.5.5 Design forces for elements of structures and use of response reduction factor

The forces on various members obtained from the elastic analysis of bridge structure are

to be divided by Response Reduction Factor given in Table 9 before combining with other

forces as per load combinations given in Table 1. The allowable increase in permissible

stresses should be as per Table 1

.

Table 9 Response Reduction Factors

Bridge ComponentR with Ductile

Detailing

R without

Ductile Detailing

Superstructure 2.0 N.A.

Substructure

(i) Masonry/PCC piers, abutments

(ii) RCC short plate piers where plastic hinge cannot

develop in direction of length and RCC abutments

(iii) RCC long piers where hinges can develop

(iv) Column(v) Beams of RCC portal frames supporting bearings

3.0

4.0

4.0

1.0

1.0

2.5

3.3

3.3

1.0

Bearings 2.0 2.0

When connectors and stoppers

are designed to withstand seismic

forces primarily, R value shall be

Connectors and Stoppers (Reaction blocks)

Those restraining dislodgement or drifting away of bridge

elements.

taken as 1 .0

When connectors and stoppers

are designed as additional safety

measures in the event of failure

of bearings, R value specified in

Table 9 for appropriate substructure

shall be adopted.

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Notes :

i) Those parts of the structural elements of foundations which are not in contact with soil

and transferring load to it, are treated as part of sub-structure element.

ii) Response reduction factor is not to be applied for calculation of displacements of

elements of bridge and for bridge as a whole.

iii) When elastomeric bearings are used to transmit horizontal seismic forces, the response

reduction factor (R) shall be taken as 1 .5 for RCC substructure and as 1 .0 for masonry

and PCC substructure.

219.6 Fully Embedded Portions

Parts of structure embedded in soil below scour level need not be considered to produce any

seismic forces.

219.7 Liquefaction

In loose sands and poorly graded sands with little or no fines, the vibrations due to earthquake

may cause liquefaction, or excessive total and differential settlements. Founding bridges on such

sands should be avoided unless appropriate methods of compaction or stabilisation are adopted.

Alternatively, the foundations should be taken deeper below liquefiable layers, to firm strata.

Reference should be made to the specialist literature for analysis of liquefaction potential.

219.8 Foundation Design

For design of foundation, the seismic loads should be taken as 1.25 times the forces

transmitted to it by substructure, so as to provide sufficient margin to cover the possible

higher forces transmitted by substructure arising out of its over strength.

219.9 Ductile Detailing

Mandatory Provisions

i) In zones IV and V, to prevent dislodgement of superstructure, "reaction blocks"

(additional safety measures in the event of failure of bearings) or other types

of seismic arresters shall be provided and designed for the seismic force

(F /R). Pier and abutment caps shall be generously dimensioned, to prevent

dislodgement of severe ground-shaking. The examples of seismic features

shown in Figs. 14 to 16 are only indicative and suitable arrangements will have

to be worked out in specific cases.

ii) To improve the performance of bridges during earthquakes, the bridges in

Seismic Zones III, IV and V may be specifically detailed for ductility for which

IRC:112 shall be referred.

Recommended Provisions

i) In order to mitigate the effects of earthquake forces described above, special

seismic devices such as Shock Transmission Units, Base Isolation, Seismic

Fuse, Lead Plug, etc, may be provided based on specialized literature,

international practices, satisfactory testing etc.

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ii) Continuous superstructure (with fewer number of bearings and expansion

joints) or integral bridges (in wiiich the substructure or superstructure are madejoint less, i.e. monolithic), if not unsuitable otherwise, can possibly provide high

ductility leading to bvetter behaviour during earthquake.

iii) Where elastomeric bearings are used, a separate system of arrester control in

both directions may be introduced to cater to seismic forces on the bearing.

REACTION BLOCKS

HALF PLAN OF

PIER CAP P2

BOX GIRDER

SUPERSTRUCTURE

r PIER CAP

HALF PLAN OF

PIER CAP P3, Ai ,A2

FREE

oz

m

P2—

RESTRAINED

P3

FREE

ELEVATION

QUlZ

IS

PLAN

FREE

oill

z

(0It]

Fig. 14 Example of Seismic Reaction Blocks for Continuous Superstructure

REACTION BLOCK

Fig. 15 Example of Seismic Reaction Blocks for Simply Supported Bridges

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IRC:6-2014

. AT ARTICULATIONS AT pilR?

WHERE :

N = N1 = N2 = 305 + 2.5L + 10 H mmL = SPAN IN METERSH = AVERAGE COLUMN HEIGHT IN METERS

Fig. 16 Minimum Dimension for Support

220 BARGE IMPACT ON BRIDGES

220.1 General

1) Bridges crossing navigable channels of rivers, creeks and canals as well as the

shipping channels in port areas and open seas shall be provided with "navigation

spans" which shall be specially identified and marked to direct the waterway traffic

below them. The span arrangement, horizontal clearances between the inner faces

of piers within the width of the navigational channel, vertical clearances above the

air-draft of the ships/barges upto soffit of deck and minimum depth of water in the

channel below the maximum laden draft of the barges shall be decided based on the

classification of waterways as per Inland Waterways Authority of India (IWAI) or the

concerned Ports and Shipping Authorities.

2) Bridge components located in a navigable channel of rivers and canals shall be

designed for barge impact force due to the possibility of barge accidentally colliding

with the structure.

3) For bridges located in sea, and in waterways under control of ports, the bridge

components may have to be designed for vessel collision force, for which the details

of the ships/barges shall be obtained from the concerned authority. Specialist literature

may be referred for the magnitudes of design forces and appropriate design solutions.

4) The design objective for bridges is to minimize the risk of the structural failure of a

bridge component due to collision with a plying barge in a cost-effective manner and

at the same time reduce the risk of damage to the barge and resulting environmental

pollution, if any. Localized repairable damage of substructure and superstructure

components is permitted provided that

:

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IRC:6-2014

a) Damaged structural components can be inspected and repaired in a relatively

cost effective manner not involving detailed investigation, and

b) Sufficient ductility and redundancy exist in the remaining structure to prevent

consequential progressive collapse, in the event of impact.

5) The Indian waterways have been classified in 7 categories by IWAI. The vessel

displacement tonnage for each of the class of waterway is shown in Table 10. Barges

and their configurations which are likely to ply, their dimensions, the Dead Weight

Tonnage (DWT), the minimum dimensions of waterway in lean section, and minimum

clearance requirements are specified by IWAI. The latest requirements (2009) are

shown in Annex E.

Table 10 Vessel Displacement Tonnage

Class of Waterway 1 11 ill IV &v VI & VII

DWT (in Tonnes) 200 600 1000 2000 4000

Note: The total displacement tonnage of self propelled vehicle (SPV) equals the weight of the

barge when empty plus the weight of the ballast and cargo (DWT) being carried by the

barge. The displacement tonnage for barge tows shall equal the displacement tonnage of the

tug/tow barge plus the combined displacement of number of barges in the length of the tow as

shown in Annex E.

6) In determining barge impact loads, consideration shall also be given to the relationship

of the bridge to :

a) Waterway geometry.

b) Size, type, loading condition of barge using the waterway, taking into account

the available water depth, and width of the navigable channel.

c) Speed of barge and direction, with respect to water current velocities in the

period of the year when barges are permitted to ply.

d) Structural response of the bridge to collision.

7) In navigable portion of waterways where barge collision is anticipated, structures shall

be :

a) Designed to resist barge collision forces, or

b) Adequately protected by designed fenders, dolphins, berms, artificial islands,

or other sacrificial devices designed to absorb the energy of colliding vessels

or to redirect the course of a vessel, or

c) A combination of (a) and (b) above, where protective measures absorb most of

the force and substructure is designed for the residual force.

8) In non-navigable portion of the waterways, the possibility of smaller barges using these

portions and likely to cause accidental impact shall be examined from consideration of

the available draft and type of barges that ply on the waterway. In case such possibility

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IRC:6-2014

exists, the piers shall be designed to resist a lower force of barge impact caused by

the smaller barges as compared to the navigational span.

9) For navigable waterways which have not been classified by IWAI, but where barges

are plying, one of Class from I & VI should be chosen as applicable, based on the local

survey of crafts plying in the waterway. Where reliable data is not available minimumClass-I shall be assigned.

220.2 Design Barge Dimensions

A design barge shall be selected on the basis of classification of the waterway. The barge

characteristics for any waterway shall be obtained from IWAI (Ref. Annex E).

The dimensions of the barge should be taken from the survey of operating barge. Where no

reliable information is available, the same may be taken from Fig. 17.

TYPICAL BARGE CONFIGURATIONS

BARGE DIMENSIONS AS PER IWAI

Class o( WaterwayUnit 1 1 M IV V VI VI

Notation

L Length m 32.6"" 45.0 m ' M ' SST"B WkJtti m 5.0 8.0 9.0 12.0 12.0 14.0 14.0

D Depth of loaded draft m 1.0 ^2 1.5 1.8 1.8 2.5 2.5

Db Depth of Bow m 1.5 1.8 22 2.7 2.7 3.7 3.7

Dv Depth of Vessel m 1.4 1.6 2.1 2.5 2.5 3.4 3.4

Hl Head of log height m 0.3 0.4 0.4 0.5 0.5 0.7 0.7

Bow Rake Length m 3.3 4.6 6.0 T2 72 8.9 8.9

Fig. 17 Typical Barge Dimensions

220.3 Checking in Dimensional Clearances for Navigation and Location of BargeImpact Force

Fig. 18 shows the position of bridge foundations and piers as well as the position of the barge

in relation to the actual water level. The minimum and maximum water levels within which

barges are permitted to ply are shown schematically. These levels should be decided by the

river authorities or by authority controlling the navigation.

The minimum navigable level will be controlled by the minimum depth of water needed for the

plying of barges. The maximum level may be determined by the maximum water velocity in

which the barges may safely ply and by the available vertical clearances below the existing

(or planned) structures across the navigable water.

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The minimum vertical clearance for the parabolic soffit shall be reckoned above the high

flood level at a distance/section where the minimum horizontal clearance from pier face is

chosen. - «

MAX PERMITTFD WATER LEVELFOR NAVIGATION

MIN. PERMITTED WATER LEVELFOR NAVIGATION

HIGHEST BED LEVEL AT PIER(NOT CONSIDERING LOCAL SCOUR)

L = Length = Row Rake Length

Dg = Depth of Bow B = Breadth/Width of Vessel (Not shown)

D^ = Depth of Vessel D min. = Water draft for empty barge

= Head of Log Height D max. = Water draft for fully loaded barge

Hg = Height of hightest point of cabin on barge

Fig. 18 Factors Deciding Range of Location of Impact Force

Use of Fig. 18:

1) For checking Minimum Clearance below Bridge Deck :

a) HQ+(Dy-D^.^) : is maximum projection of the highest barge component above actual water

level (e.g. including projecting equipment over top of cabin like radar mast).

b) Highest Level of Barge : (HQ+(Dy-D^.^) + maximum permitted water level for navigation

(This may be decided by water current velocity). Minimum specified clearance should be

checked with reference to this level and lowest soffit level of bridge.

2) For determining lowest position of barge with respect to bridge pier.

a) Maximum depth of submergence = D = Maximum Water Draft.' r- o max

b) Minimum level permitted for navigation = Level at which minimum clearance required for

navigation between bed level and lowest part of barge (at D^^J is available.

3) For determining range of pier elevations between which barge impact can take places anywhere :

a) Highest Level = Maximum water level permitted for navigation + (D^-D^.J.

b) Lowest Level = Minimum water level permitted for navigation + (Dg-D^^J.

c) Height over which impact force Pg acts = H^^ as defined in Fig. 18.

220.4 Design Barge Speed

The speed at which the barge collides against the components of a bridge depends uponto the barge transit speed within the navigable channel limits, the distance to the location of

the bridge element from the centre line of the barge transit path and the barge length overall

(LOA). This information shall be collected from the IWAI. In absence of any data, a design

speed of 6 knots (i.e. 3.1 m/sec) for unladen barge and 4 knots (i.e. 2.1 m/sec) for laden

barge may be assumed for design for both upstream and downstream directions of traffic.

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220.5 Barge Collision Energy

KE = 500 X X W X (V)2,

where,

W = Barge Displacement Tonnage (T)

V = Barge impact speed (m/sec)

KE = Barge Collision Energy (N-m)

C^ = hydrodynamic coefficient

= 1.05 to 1.25 for Barges depending upon the underkeel clearance available.

• In case underkeel clearance is more than 0.5 x Draft, C^=1 .05;

• In case underkeel clearance is less than 0.1 x Draft, C^ = 1 .25.

• For any intermediate values of underkeel clearance, linear interpolation shall be

done.

1

Note: The formula of kinetic energy is a standard kinetic energy, equation KE=-Mv^2w ^

Mass, M = —where W is the weight of barge and C^ is the hydro dynamic effectg

representing mass of the water moving together with the barge. Substituting value in

proper units in K.E. formula yields the equation given in the draft.

220.6 Barge Damage Depth, 'a^'

3^= 3100 X( [1 + 1.3 X 10<-^)x KEP- 1),

where,

ag = Barge bow damage depth (mm)

220.7 Barge Collision Impact Force, 'Pg'

The barge collision impact force shall be determined based on the following equations:

For ag<1 00 mm, Pg = 6.0 x 1 0^ x (a^), in N

For ag> 100 mm, Pg = 6.0 X 10^ + 1600 X (ag), in N

220.8 Location & Magnitude of Impact Force in Substructure & Foundation, 'P^'

All components of the substructure, exposed to physical contact by any portion of the design

barge's hull or bow, shall be designed to resist the applied loads. The bow overhang, rake,

or flair distance of barges shall be considered in determining the portions of the substructure

exposed to contact by the barge. Crushing of the barge's bow causing contact with any

setback portion of the substructure shall also be considered.

Some of the salient barge dimensions to be checked while checking for the navigational

clearances are as follows :

63

IRC:6-2014

The design impact force for the above cases is to be applied as a vertical line load equally

distributed along the barge's bow depth, H2 defined with respect to the reference water level,

as shown in Fig. 18. The barge's bow is considered to be raked forward in determining the

potential contact area of the impact force on the substructure.

220.9 Protection of Substructures

Protection may be provided to reduce or to eliminate the exposure of bridge substructures to

barge collision by physical protection systems, including fenders, pile cluster, pile-supported

structures, dolphins, islands, and combinations thereof.

Severe damage and/or collapse of the protection system may be permitted, provided that

the protection system stops the Barge prior to contact with the pier or redirects the bargeaway from the pier. In such cases, the bridge piers need not be designed for Barge Impact.

Specialist literature shall be referred for design of protection structures.

Flexible fenders or other protection system attached to the substructure help to limit the

damage to the barge and the substructure by absorbing part of impact (kinetic energy of

collision). For the design of combined system of pier and protection system, the design forces

as obtained from Clause 220.7 shall be used in absence of rigorous analysis.

220.10 Load Combination

The barge collision load shall be considered as an accidental load and load combination shall

conform to the provisions of IRC:6. Barge impact load shall be considered only under Ultimate

Limit State. For working load/allowable stress condition, allowable stress may be increased by

50 percent.

The probability of the simultaneous occurrence of a barge collision together with the maximumflood need not be considered. For the purpose of load combination of barge collision, the

maximum flood level may be taken as the mean annual flood level of previous 20 years,

provided that the permissible maximum current velocities for the barges to ply are not

exceeded. In such event maximum level may be calculated backward from the allowable

current velocities. The maximum level of scour below this flood level shall be calculated by

scour formula in Clause 703.3.1 of IRC:78. However, no credit for scour shall be taken for

verifying required depth for allowing navigation.

221 SNOW LOAD

The snow load of 500 kg/m^ where applicable shall be assumed to act on the bridge deckwhile combining with live load as given below. Both the conditions shall be checkedindependently:

a) A snow accumulation upto 0.25 m over the deck shall be taken into

consideration, while designing the structure for wheeled vehicles.

b) A snow accumulation upto 0.50 m over the deck shall be taken into

consideration, while designing the structure for tracked vehicles.

c) In case of snow accumulation exceeding 0.50 m, design shall be based on the

maximum recorded snow accumulation (based on the actual site observation,

including the effect of variation in snow density). No live load shall be considered

to act along with this snow load.

64

IRC:6-2014

222 VEHICLE COLLISION LOADS ON SUPPORTS OF BRIDGES,FLYOVER SUPPORTS AND FOOT OVER BRIDGES

222.1 General

222.1.1 Bridge piers of wall type, columns or the frames built in the median or in the vicinity of

the carriageway supporting the superstructure shall be designed to withstand vehicle collision

loads. The effect of collision load shall also be considered on the supporting elements, such as,

foundations and bearings. For multilevel carriageways, the collision loads shall be considered

separately for each level.

222.1 .2 The effect of collision load shall not be considered on abutments or on the structures

separated from the edge of the carriageway by a minimum distance of 4.5 m and shall also not

be combined with principal live loads on the carriageway supported by the structural memberssubjected to such collision loads, as well as wind or seismic load. Where pedestrian/cycle

track bridge ramps and stairs are structurally independent of the main highway-spanning

structure, their supports need not be designed for the vehicle collision loads.

Note : The tertiary structures, such as lighting post, signage supports etc. need not be designed

for vehicle collision loads.

222.2 Increase in Permissible Stress

The permissible stresses in both steel and concrete shall be increased by 50 percent and the

safe bearing capacity of the founding strata increased by 25 percent when considering the

effect of collision loads.

222.3 Collision Load

222.3.1 The nominal loads given in Table 11 shall be considered to act horizontally as

Vehicle Collision Loads. Supports shall be capable of resisting the main and residual load

components acting simultaneously. Loads normal to the carriageway below and loads parallel

to the carriageway below shall be considered to act separately and shall not be combined.

Table 11 Nominal Vehicle Collision Loads on Supports of Bridges

Load Normal to the

Carriageway Below (Ton)

Load Parallel to the

Carriageway Below (Ton)

Point of Application onBridge Support

Main load

component50 100

At the most severe point

between 0.75 and 1.5 mabove carriageway level

Residual

load

component

25

(10)

50

(10)

At the most severe point

between 1 m and 3 mabove carriageway level

Note : Figures within brackets are for FOBs.

65

IRC:6-2014

222.3.2 The loads indicated in Clause 222.3.1 , are assumed for vehicles plying at velocity of

about 60 km/hour. In case of vehicles travelling at lesser velocity, the loads may be reduced

in proportion to the square of the velocity but not less than 50 percent.

222.3.3 The bridge supports shall be designed for the residual load component only, if

protected with suitably designed fencing system taking into account its flexibility, having a

minimum height of 1 .5 m above the carriageway level.

223 INDETERMINATE STRUCTURES AND COMPOSITESTRUCTURES

Stresses due to creep, shrinkage and temperature, etc. should be considered for statically

indeterminate structures or composite members consisting for steel or concrete prefabricated

elements and cast-in-situ components for which specialist literature may be referred to. Creep

and shrinkage produce permanent stresses and hence no relaxation in permissible stresses

shall be allowed.

66

Annex A(Clause 201.2)

IRC:6-2014

TRACKED VEHICLES . WHEELED VEHICLES

Class

Width

of

track

Width

over

trockFour wheelers

Vovsingle

a«leload

Six whoelerssinale

axleload

âx boîe

load Minimum wheel spacing and tyre sizes of critical (Heaviest) oxies.

Max. tyre loodon min.tyre size.

Mox.lyrepressure Remarks

0 c d e f 9 h i k 1 m P q

i

1.8t

1.1 t

2.42t

l,Ot0.55 1 on

col. (k)

150x410

2.46

kg/cm^

).7 l.fT

. 1W0 pio,

IMO, ,

,

a to

ft-TTo-e

SA 150 X 410

5R

5Sl

230 1980

5.5 I

3.4 t

5.4t

2.2t 4.4t

SA for (f) 220x510

0 1750 9

MJStt1.7 t on

220x410

4.218

kg/cm1990

Nose to toil

Length 3660

2.1 iA3050 no

_

Y.o 12Y.f1»j, J!00 .jl,2», 010 SA 190 X 410

BA 190 X 410

W ,7.0 DO

SA ISO x410 (f)4(h)

BA. 150 X 410

9R

9.5t

300 2130

9,2 tlot

3.5t 7.01

SA. for (f) 300x510

gfl BO ,.,0 OB

2.9 t on

250x510

5.273

kg/cm2740

Nose to toil

Length 4270

* W )10

ua 3.5

3300

^ 1^1220 SA 230 X 510

BA 230 X 610SA220 <510 lor (1)

SA150 x5106A1S0 K 510

12R

li.St

300 2290

12t

7.5 t

12t

4.6t 9,6t

SA. for (f) 360x510

B 2H0 8

516^434

3.75t on

360x610

5.273

kg/cm^2740

Nose to toil

Length 4880

' f)I0

L3200

,

' ,i1220 SA 250 X 510

BA 250 X 510

00 2«o DO

5*230 «510 (or (1)

SA190 x5106A190 X 510

18R

191

360 2360 10.0 t

18.7tt

7.6t 15.2t

SA. for (f) 410x6100 2,30 n

S.OOt on

410x610

5.273

kg/cmNose to toil

Length 54904270 no fi.f^

»«,'']7,(

t220 SIO SA 360 X 510BA 360 X 510

SA230 x5I0 lor (t)

SA220 x5106A220 X 510

24R

251

360 2440

20t

12.0t

21.2t

8.5t 17 Ot

SA for (f) 410x610Q

22TO 0 0 U "

SA.300 x5lO for (()

SA.230 x5lO

6.00t on

410x610

5.273

kg/cm3660

Nose to toil

Length 5490

'"'?

pio0 12.<

4270 . <«\. 104.2 U

3W0 ,

BJ1220 BIO SA 410 X 610

BA 410 X 610

SA.300 xSlO lor (1)

SA230 x510BA230 X 510

30R

Jot

410 2590

38 t

14.0 t 20 t

Axle sfMxing

1220

JB^SIO,

2*40,

7 OOt on

530x610

5.273

kg/cm3660

Nose to toil

Length 6440

P'O 3Ut>of 10.0Y ,oY

SA. 530 X 61OSA 460 X SIO

DO 2M0 OB

SA360 x510

BA230 X SIO

SA.360 xSIO

BA.230 X 510

DO DD DO nLcLJOO

SA.190 x510

BA.190 X 510

40R

40t

560 2740

55 t

16.0 t

26 t

Axle spacing

1070

!U^jl6

on nntJD 25,0 UU

SA360 x610

BA300 X 510

,f ** 2510

,8. OOt on530x610

single oxie col.(l<]

for wind fttfBct The•ngth o( vehicle moybe ossumed 2440

5.273

kg/cm1

3660

Nose to toil

Length 7320.f'op mo .j'^.j 1 1

BIO SA. 530 X 610BA. 460 X 610

SA.160 x510

ftHiOO X 510

00 DD 0 n

SA.190 K510

aA.190 X 510

50R

50t

610 2790

65.5 t

17.5 t

32 t

Axle spocing

1070

1.25flO

,25BO

OIT TO5.273

, 2kg/cm

Actual max. tyre load

4.38 t on 410x6104270

Nose to toil

Length 7540-J.

0, 3M0

,

ijof %i tsif'

2» «««1

«!70 ^ 1070

S.3

BIO

BB-iar-i

SA410 x610

BA300 X 610

D U "

SA410 xSIO

GA360 X 610

DO H] ODÔD

SA190 x510

aAigo X 510

60R

601

760 2840

74 t

19.0 t

36 t

Axle spocing

1070

,2670

,

0 U "

Sk.410 «610

BA410 X 610

2S701

DIT TO5.273^

kg/cm

Actual max. tyre load

4.75 t on 410x6104570

Nose to toil

Length 7920

,*a.o 7^1 7.5Y "Sl.O I8.df*

- .|. *P' .l.ifo.

iB,0

810

OB 2070 OB

SA410 x610

BA410 X 610

00 DD DD DD

SA. 22Q xSIO

BA. 220 X 510

70R

701

640 2900

100 t 20 t 40 t

w}^ So o

1Jj iJ iiL

,2780

1 1

OIT TO5.273

kg/cm

Actual mox, tyre lood

5.0 t on 410x6104570

Nose to toil

Length 7920

LO 12.0f,.IJ.0Y 1'J'20

1

21J0njff* i7i}f 17.

. »» .IjJTft

HBl(\

BB-TsHB

SA410 x610

BA410 X 610

0 0

SA410 >610

VL4I0 I 610

.,J DO DD DD

SA 230 x510

e«. 230 X 510

67

IRC:6-2014

222.3.2 Theloa<

about 60 km/hou

in proportion to ti

222.3.3 Tine brii

protected with si

minimum height i

223 I

Stresses due to

indeterminate str

elements and cas

and shrinkage pr

shall be allowed.

Annex A(Clause 201.2)

IRC:6-2014

HYPOTHETICAL VEHICLES FOR CLASSIFICATION OF VEHICLESAND BRIDGES (REVISED)

NOTES FOR LOAD CLASSIFICATION CHART

1) The possible variations in the wheel spacings and tyre sizes, for the heaviest

single axles-cols, (f) and (h), the heaviest bogie axles-col. (j) and also for the

heaviest axles of the train vehicle of cols, (e) and (g) are given in cols, (k), (I),

(m) and (n). The same pattern of wheel arrangement may be assumed for all

axles of the wheel train shown in cols, (e) and (g) as for the heaviest axles. The

overall width of tyre in mm may be taken as equal to [150+(p-1) 57], where "p"

represents the load on tyre in tonnes, wherever the tyre sizes are not specified

on the chart.

2) Contact areas of tyres on the deck may be obtained from the corresponding

tyre loads, max. tyre pressures (p) and width of tyre treads.

3) The first dimension of tyre size refers to the overall width of tyre and second

dimension to the rim diameter of the tyre. Tyre tread width may be taken as

overall tyre width minus 25 mm for tyres upto 225 mm width, and minus 50 mmfor tyres over 225 mm width.

4) The spacing between successive vehicles shall not be less than 30 m. This

spacing will be measured from the rear-most point of ground contact of the

leading vehicles to the forward-most point of ground contact of the following

vehicle in case of tracked vehicles. For wheeled vehicles, it will be measured

from the centre of the rear-most axle of the leading vehicle to the centre of the

first axle of the following vehicle.

5) The classification of the bridge shall be determined by the safe load carrying

capacity of the weakest of all the structural members including the main girders,

stringers (or load bearers), the decking, cross bearers (or transome) bearings,

piers and abutments, investigated under the track, wheel axle and bogie loads

shown for the various classes. Any bridge upto and including class 40 will be

marked with a single class number-the highest tracked or wheel standard load

class which the bridge can safely withstand. Any bridge over class 40 will be

marked with a single class number if the wheeled and tracked classes are the

69

same, and with dual classification sign showing both T and W load classes if

the T and W classes are different.

The calculations determining the safe load carrying capacity shall also allow for

the effects due to impact, wind pressure, longitudinal forces, etc., as described

in the relevant Clauses of this Code.

The distribution of load between the main girders of a bridge is not necessarily

equal and shall be assessed from considerations of the spacing of the main

girders, their torsional stiffness, flexibility of the cross bearers, the width

of roadway and the width of the vehicles, etc., by any rational method of

calculations.

The maximum single axle loads shown in columns (f) and (h) and the bogie

axle loads shown in column (j) correspond to the heaviest axles of the trains,

shown in columns (e) and (g) in load-classes upto and including class 30-R. In

the case of higher load classes, the single axle loads and bogie axle loads shall

be assumed to belong to some other hypothetical vehicles and their effects

worked out separately on the components of bridge deck.

The minimum clearance between the road face of the kerb and the outer edge

of wheel or track for any of the hypothetical vehicles shall be the same as for

Class AA vehicles, when there is only one-lane of traffic moving on a bridge. If

a bridge is to be designed for two-lanes of traffic for any type of vehicles given

in the Chart, the clearance may be decided in each case depending upon the

circumstances.

70

IRC:6-2014

NOTES FOR LOAD CLASSIFICATION CHART

QQ1

1

1

1

SO.OM 1

Uin*

TJ08»._,jj..„.,J

TRACKED VEHICLE

TRACKED VEHICLE

.tjfmmmmm..."5« Wn.

Notes

WHEELED VEHICLE

Fig. 1A Class AATracked and Wheeled Vehicles (Clause 204.1)

1) The nose to tail spacing between two successive vehicles shall not be less than 90m.

2) For multi-lane bndges and culverts, each Class AA loading shall be considered to occupy

two lanes and no other vehicle shall be allowed in these two lanes. The passing/crossing

vehicle can only be allowed on lanes other than these two lanes. Load combination is as

shown in Table 2.

3) The maximum loads for the wheeled vehicle shall be 20 tonne for a single axle or 40

tonne for a bridge of two axles spaced not more than 1 .2 m centres.

4) Class AA loading is applicable only for bridges having carriageway width of

5.3 m and above (i.e. 1.2 x 2 + 2.9 = 5.3). The minimum clearance between

the road face of the kerb and the outer edge of the wheel or track, 'C, shall be

1.2 m.

5) Axle loads in tone. Linear dimensions in metre.

71

IRC:6-2014

Annex B(Clause 202.3)

COMBINATION OF LOADS FOR LIMIT STATE DESIGN

1 Loads to be considered while arriving at the appropriate combination for carrying out

the necessary checks for the design of road bridges and culverts are as follows:

1 ) Dead Load

2) Snow load (See note i)

3) Superimposed dead load such as hand rail, crash barrier, foot path and service

loads.

4) Surfacing or wearing coat

5) Back Fill Weight

6) Earth Pressure

7) Primary and secondary effect of prestress

8) Secondary effects such as creep, shrinkage and settlement.

9) Temperature including restraint and bearing forces.

10) Carriageway live load, footpath live load, construction live loads.

11) Associated carriageway live load such as braking, tractive and centrifugal

forces.

12) Accidental effects such as vehicle collision load, barge impact and impact due

to floating bodies.

13) Wind

14) Seismic Effect

15) Erection effects

16) Water Current Forces

17) Wave Pressure „

'

18) Buoyancy

Notes

i) The snow loads may be based on actual observation or past records in the particular

area or local practices, if existing

ii) The wave forces shall be determined by suitable analysis considering drawing

and inertia forces etc. on single structural members based on rational methods or

model studies. In case of group of piles, piers etc., proximity effects shall also be

considered.

72

IRC:6-2014

2 Combination of Loads for the Verification of Equilibrium and Structural

Strength under Ultimate State

Loads are required to be combined to check the equilibrium and the structural strength under

ultimate limit state. The equilibrium of the structure shall be checked against overturning, sliding

and uplift. It shall be ensured that the disturbing loads (overturning, sliding and uplifting) shall

always be less than the stabilizing or restoring actions. The structural strength under ultimate

limit state shall be estimated in order to avoid internal failure or excessive deformation. Theequilibrium and the structural strength shall be checked under basic, accidental and seismic

combinations of loads.

3 Combination Principles

The following principles shall be followed while using these tables for arriving at the

combinations:

i) All loads shown under Column 1 of Table 3.1 or Table 3.2 or Table 3.3 or

Table 3.4 shall be combined to carry out the relevant verification.

ii) While working out the combinations, only one variable load shall be considered

as the leading load at a time. All other variable loads shall be considered as

accompanying loads. In case if the variable loads produce favourable effect

(relieving effect) the same shall be ignored.

iii) For accidental combination, the traffic load on the upper deck of a bridge (when

collision with the pier due to traffic under the bridge occurs) shall be treated as

the leading load. In all other accidental situations the traffic load shall be treated

as the accompanying load.

iv) During construction the relevant design situation shall be taken into account.

v) These combinations are not valid for verifying the fatigue limit state.

4 Basic Combination

4.1 For Checking the Equilibrium

For checking the equilibrium of the structure, the partial safety factor for loads shown in

Column No. 2 or 3 under Table 3.1 shall be adopted.

4.2 For Checking the Structural Strength

For checking the structural strength, the partial safety factor for loads shown in ColumnNo. 2 under Table 3.2 shall be adopted.

5 Accidental Combination


Column No. 4 or 5 under Table 3.1 and for checking the structural strength, the partial safety

factor for loads shown in Column No. 3 under Table 3.2 shall be adopted.

73

IRC:6-2014

6 Seismic Combination


Column No. 6 or 7 under Table 3.1 and for checking the structural strength, the partial safety

factor for loads shown in Column No. 4 under Table 3.2 shall be adopted.

7 Combination of Loads for the Verification of Serviceability Limit State

Loads are required to be combined to satisfy the serviceability requirements. The serviceability

limit state check shall be carried out in order to have control on stress, deflection, vibration,

crack width, settlement and to estimate shrinkage and creep effects. It shall be ensured that

the design value obtained by using the appropriate combination shall be less than the limiting

value of serviceability criterion as per the relevant code. The rare combination of loads shall

be used for checking the stress limit. The frequent combination of loads shall be used for

checking the deflection, vibration and crack width. The quasi-permanent combination of loads

shall be used for checking the settlement, shrinkage creep effects and the permanent stress

in concrete.

7.1 Rare Combination

For checking the stress limits, the partial safety factor for loads shown in Column No. 2 under

Table 3.3 shall be adopted.

7.2 Frequent Combination

For checking the deflection, vibration and crack width in prestressed concrete structures,

partial safety factor for loads shown in column no. 3 under Table 3.3 shall be adopted.

7.3 Quasi-permanent Combinations

For checking the crack width in RCC structures, settlement, creep effects and to estimate

the permanent stress in the structure, partial safety factor for loads shown in Column No. 4

under Table 3.3 shall be adopted.

8 Combination for Design of Foundations

For checking the base pressure under foundation and to estimate the structural strength

which includes the geotechnical loads, the partial safety factor for loads for 3 combinations

shown in Table 3.4 shall be used.

The material safety factor for the soil parameters, resistance factor and the allowable bearing

pressure for these combinations shall be as per relevant code.

74

IRC:6-2014

Table 3.1 Partial Safety Factor for Verification of Equilibrium

Loads Basic CombinationAccidental

CombinationSeismic Combination

(1)

Ovprti irninnVa/ Vd lUI 1 III 1^

or Sliding

or Uplift

Effect

Rpctnrinn

or Resisting

Effect

Ovprti irninn\J VCI LUI 1 ill lU

or Sliding

or Uplift

Effect

RpQtnrinfi

or Resisting

Effect

Ox/prti irninn

or Sliding

or Uplift

Effect

Dpctnrinn

or Resisting

Effect

Permanent Loads:Dead Load, Snow load if present,

SIDL except surfacing, Backfill

weight, settlement, creep andshrinkage effect

1.05 0.95 1.0 1.0 1.05 0.95

Surfacing 1.35 1.0 1.0 1.0 1.35 1.0

Prestress and Secondary effect of

prestress

(Refer Note 5)

Earth pressure due to Back Fill 1.50 - 1.0 - 1.0 -

Variable Loads

:

Carriageway Live Load, associated

loads (braking, tractive andcentrifugal forces) and Pedestrian

Live Load(a) As Leading Load(b) As accompanying Load(c) Construction Live Load

1.5

1.15

0

0

U

0.75

0.2

1 .U

0

0

U

0.21 A

0

U

Thermal Loads(a) As Leading Load(b) As accompanying Load

1.50

0.9

0

0 0.5 0 0.5 0

Wind(a) As Leading Load(b) As accompanying Load

1.5

0.9

0

0

- - - -

Live Load Surcharge effects (as

accompanying load)

1.20 0

Accidental effects:

i) Vehicle collision (or) 1

ii) Barge Impact (or) \

iii) Impact due to floating bodies J

1.0

Seismic Effect

(a) During Service

(b) During Construction

- - - - 1.5

0.75

-

Construction Condition:

Counter Weights:a) When density or self weight is well

defined

b) When density or self weight is not

well defined

c) Erection effects 1.05

0.9

0.8

0.95 _

1.0

1.0

-

1.0

1.0

Wind(a) Leading Load(b) Accompanying Load

1.50

1.20

0

0

Hydraulic Loads:(Accompanying Load):Water current forces

1.0

0 1.0 1.0

Wave PressureHydrodynamic effect

Buoyancy

1.0

1.0

0 1.0

1.0

1.0

1.0

1.0

75

During launching tlie counterweigiit position shall be allowed a variation

of ± 1 m for steel bridges.

For Combination principles refer Para 3.

Thermal effects include restraints associated with expansion/contraction due to type

of construction (Portal frame, arch and elastomeric bearings), frictional restraint in

metallic bearings and thermal gradients. This combination however, is not valid for

the design of bearing and expansion joint.

Wind load and thermal load need not be taken simultaneously.

Partial safety factor for prestress and secondary effect of prestress shall be as

recommended in the relevant codes.

Wherever Snow Load is applicable. Clause 221 shall be referred for combination of

snow load and live load.

Seismic effect during erection stage is reduced to half when construction phase

does not exceed 5 years.

For repair, rehabilitation and retrofitting, the load combination shall be project

specific.

For calculation of time period and seismic force, dead load, SIDL and appropriate

live load as defined in Clause 219.5.2, shall not be enhanced by corresponding

partial safety factor as given in Table 3.1 and shall be calculated using unfactored

loads.

76

IRC:6-2014

Table 3.2 Partial Safety Factor for Verification of Structural Strength

Ultimate Limit State

Loads Basic

Combination

Accidental

CombinationSeismic

Combination

(1) (2) (3) (4)

Permanent Loads:

Dead Load, Snow load if present, SIDL except surfacing

a) Adding to tiie effect of variable loads

b) Relieving the effect of variable loads

1.35

1.0

1.0

1.0

1.35

1.0

Surfacing:

Adding to the effect of variable loads

Relieving the effect of variable loads

1.75

1.0

1.0

1.0

1.75

1.0

Prestress and Secondary effect ofprestress

(refer note no. 2)

Back fill Weight 1.50 1.0 1.0

Eartti pressure due to Back Fill

a) Leading Load

b) Accompanying Load

1.50

1.0 1.0

1.0

1.0

Variable Loads:

Carriageway Live Load and associated loads (braking,

tractive and centrifugal forces) and

Pedestrian Live Load:

a) Leading Load


c) Construction Live Load

1.5

1.15

1.35

0.75

0.2

1.0

0

0.2

1.0

Wind during service and construction

a) Leading Load


1.50

0.9

Live Load Surcharge (as accompanying load) 1.2 0.2 0.2

Erection effects 1.0 1.0 1.0

Accidental Effects:

i) Vehicle Collision (or) îi) Barge Impact (or) riii) Impact due to floating bodies J

- 1.0 -

Seismic Effect

a) During Service

b) During Construction

- - 1.5

0.75

Hydraulic Loads (Accompanying Load):

Water Current Forces

Wave Pressure

Hydrodynamic effect

Buoyancy

1.0

1.0

0.15

1.0

1.0

0.15

1.0

1.0

1.0

0.15

77

IRC:6-2014

Notes :

1) For combination principles, refer Para 3.

2) Partial safety factor for prestress and secondary effect of prestress shall be as


3) Wherever Snow Load is applicable, Clause 221 shall be referred for

combination of snow load and live load.

4) For calculation of time period and seismic force, dead load, SIDL and appropriate

live load as defined in Clause 219.5.2, shall not be enhanced by corresponding

partial safety factor as given in Table 3.2 and shall be calculated using unfactored

loads.

Table 3.3 Partial Safety Factor for Verification of Serviceability Limit State

Loads Rare Combination Frequent

CombinationQuasi-permanentCombination

(1) (2) (3) (4)

Permanent Loads:

Dead Load, Snow load if present,

SIDL including surfacing 1.0 1.0 1.0

Back fill Weight 1.0 1.0 1.0

Prestress and Secondary effect of prestress

(refer note no. 4)

Shrinkage and Creep Effects 1.0 1.0 1.0

Earth Pressure due to Back Fill 1 .(J 1 .0 1.0

Settlement Effects

a) Adding to the permanent loads

b) Opposing the permanent loads

1.0

0

1.0

0

1.0

0

Variable Loads:

Carriageway Live Load and associated

loads(braking, tractive and centrifugal forces) and

Pedestrian Live Load

a) Leading Load


1.0

0.75

0.75

0.2 0.

Thermal Loadsa) Leading Load


1.0

0.6

0.6

0.5 0.5

Winda) Leading Load


1.0

0.60

0.60

0.50 0

Live Load Surcharge (Accompanying Load) 0.80 0 0

Hydraulic Loads (Accompanying Load):

Water Current Forces

Wave Pressure

Buoyancy

1.0

1.0

0.15

1.0

1.0

0.15 0.15

78

IRC:6-2014

Notes :

1) For Combination principles, refer Para 3.

2) Tliermal load includes restraints associated with expansion/ contraction due to type

of construction (Portal frame, arch and elastomeric bearings), frictional restraint in

metallic bearings and thermal gradients. This combination however, is not valid for

the design of bearing and expansion joint.

3) Wind and thermal loads need not be taken simultaneously.

4) Partial safety factor for prestress and secondary effect of prestress shall be as


5) Where Snow Load is applicable, Clause 221 shall be referred for combination of


Table 3.4 Combination for Base Pressure and Design of Foundation

Loads Combination

(1)

Combination

(2)

Seismic

CombinationAccidental

Combination

(2) (3)

Permanent Loads:

Dead Load, Snow load if present, SIDL except surfacing,

Bacl< Fill earth filling 1.35 1.0 1.35 1.0

SIDL Surfacing 1.75 1.0 1.75 1.0

Pre-stress Effect

(refer note 4)

Settlement Effect 1.0 or 0 1.0 or 0 I.OorO I.OorO

Earth Pressure due to back fill

a) Leading Load


1.50

1.0

1.30

0.85 1.0 1.0

Variable Loads:

All carriageway loads and associated loads (braking,

tractive and centrifugal) and pedestrian load

a) Leading Load 1.5 1.3 (0.75 if applicable)

orO(0.75 if applicable)

orO

b) Accompanying Load 1.15 1.0 0.2 0.2

Thermal Loads as accompanying load 0.90 0.80 0.5 0.5

Winda) Leading Load


1.5

0.9

1.3

0.80 0 0

Live Load Surcharge as Accompanying Load

(if applicable)

1.2 1.0 0.2 0.2

Accidental Effect or Seismic Effect

Seismic effect during construction

a) During Service

b) During Construction

1.5

0.75

1.0

0.5

Erection effects 1.0 1.0 1.0 1.0

Hydraulic Loads:Water Current

Wave Pressure

Hydrodynamic effect

Buoyancy:

For Base Pressure

For Structural Design

1.0 or 0

1.0 or 0

1.0

0.15

1.0 or 0

1.0 or 0

1.0

0.15

I.OorO

1.0 or 0

I.OorO

1.0

0.15

1.0 or 0

1.0 or 0

1.0 or 0

1.0

0.15

79

For combination principles, refer para 3.

Where two partial factors are indicated for loads, both these factors shall be considered

for arriving at the severe effect.

Wind and Thermal effects need not be taken simultaneously.

Partial safety factor for prestress and secondary effect of prestress shall be as


Wherever Snow Load is applicable, Clause 221 shall be referred for combination of


Seismic effect during erection stage is reduced to half when construction phase does

not exceed 5 years. '

For repair, rehabilitation and retrofitting the load combination shall be project specific.

For calculation of time period and seismic force, dead load, SIDL and appropriate live

load as defined in Clause 219.5.2. shall not be enhanced by corresponding partial

safety factor as given in Table 3.4 and shall be calculated using unfactored loads.

At present the combination of loads shown in Table 3.4 shall be used for structural

design of foundation only. For checking the base pressure under foundation unfactored

loads shall be used. Table 3.4 shall be used for checking of base pressure under

foundation only when the relevant material safety factor and resistance factor are

introduced in IRC:78.

80

Annex C(Clause 209.3.3)

IRC:6-2014

Wind Load Computation on Truss Bridge Superstructure

C-1.1 Superstructures without live load: The design transverse wind load sliall be

derived separately for the areas of the windward and leeward truss girder and deck elements.

Except that need not be derived considering the projected areas of windward parapet

shielded by windward truss, or vice versa, deck shielded by the windward truss, or vice versa

and leeward truss shielded by the deck.

The area for each truss, parapet etc. shall be the solid area in normal projected elevation.

The area for the deck shall be based on the full depth of the deck.

C-1.2 Superstructures with live load: The design transverse wind load shall be derived

separately for elements as specified in C-1 and also for the live load depth. The area A^ for

the deck, parapets, trusses etc. shall be as for the superstructure without live load. The area

A^ for the live load shall be derived using the appropriate live load depth.

C-1 .3 Drag Coefficient for All Truss Girder Superstructures

a) Superstructures without live load: The drag coefficient for each truss and for

the deck shall be derived as follows:

For a windward truss shall be taken from Table C-1 . For leeward truss of a superstructure

with two trusses, drag coefficient shall be taken as t/C^. Values of shielding factor rj are given

in Table C-2. The solidity ratio of the truss is the ratio of the effective area to the overall area

of the truss.

Where a superstructure has more than two trusses, the drag coefficient for the truss adjacent

to the windward truss shall be derived as specified above. The coefficient for all other trusses

shall be taken as equal to this value.

For Deck Construction, the drag coefficient shall be taken as 1 .1

.

b) Superstructure with live load: The drag coefficient for each truss and for the

deck shall be as for the superstructure without live load. for the unshielded parts

of the live load shall be taken as 1 .45.

81

IRC:6-2014

Table C-1 Force Coefficients for Single Truss

Solidity

Ratio

(O)

Drag Coefficient for

Built-up

SectionsRounded Members of Diameter (d)

Subcritical flow

(dV^< 6m2/s)

Supercritical flow

(dV^ > 6m2/s)

0.1 1.9 1.2 0.7

0.2 1.8 1.2 0.8

0.3 1.7 1.2 0.8

0.4 1.7 1.1 0.8

0.5 1.6 1.1 0.8

Notes

:

1) Linear interpolation between values is permitted.

2) The solidity ratio of the truss is the ratio of the net area to overall area of the truss

Table C-2 Shielding Factor i] for Multiple Trusses

^ . Truss Spacing Ratio

Value of 1] for Solidity Ratio

0.1 0.2 0.3 0.4 0.5

<1 1.0 0.90 0.80 0.60 0.45

2 1.0 0.90 0.80 0.65 0.50

3 1.0 0.95 0.80 0.70 0.55

4 1.0 0.95 0.85 0.70 0.60

5 1.0 0.95 0.85 0.75 0.65

6 1.0 0.95 0.90 0.80 0.70

Notes :

1 ) Linear interpolation between values is permitted.

2) The truss spacing ratio is the distance between centers of trusses divided by

depth of the windward truss.

82

IRC:6-2014

Annex D(Clause 219.5)

The fundamental natural period T (in seconds) of pier/abutment of the bridge along a horizontal

direction may be estimated by the following expression:

D = Appropriate dead load of the superstructure and live load in kN

F = Horizontal force in kN required to be applied at the centre of mass of

superstructure for one mm horizontal deflection at the top of the pier/

abutment for the earthquake in the transverse direction; and the force

to be applied at the top of the bearings for the earthquake in the longitudinal

direction.

where,

83

IRC:6-2014

Annex E(Clause 220.1)

CLASSIFICATION OF INLAND WATERWAYS IN INDIA

Class of

Waterway

Tonnage

(DWT)of SPV

(T)

Barge Units Minimum Dimensions of Navigational Channels in

Lean SeasonsMinimum Clearances for cross

structure

Dimension

of Single

Barge

(m)

Dennensionof

Barge Units

(m)

Tonnage

of Barge

Units

(DWT)(T)

Rivers Canals

Radius

(m)

Horizontal Clearance

Vertical

V-'iydrdllL-C

(m)

Depth*

(m)

Bottom

Width

(m)

Depth*

(m)

Bottom

Width

(m)

Rivers

(m)

Canals

(m)

1 100 32x5x1.0

80x5x1.0

^ 1 1

200 1.20 30 1.50 20 300 30 20 4.0

II 300 45x8x1.2

110x8x1.2

^ 1 1

600 1.40 40 1.80 30 500 40 30 5.0

III 500 58x9x1.5

141x9x1.5

^ 1 1

1000 1.70 50 2.20 40 700 50 40 7.0

IV 1000 70x12x1.6

170x12x1.8

^ 1 1

2000 2.00 50 2.50 50 800 50 50 10.0

V 1000 70x12x1.6

170x24x1.8

4000 2.00 80 800 80 10.0cz

VI 2000 86x14x2.5

21 0x14x2.5

4000 2.75 80 3.50 60 900 80 60 10.0

1

VII 2000 86x14x2.5

210x26x2.5

8000 2.75 100 900 100 10.0

cz:

Note

:

1) SPV : Self Propelled Vehicle : L-Overall Length ; B-Beam Width; D-Loaded Draft

2) Minimum Depth of Channel should be available for 95% of the year

3) The vertical clearance shall be available in at least 75% of the portion of each of the

spans in entire width of the waterway during lean season. .

4) Reference levels for vertical clearance in different types of channels is given below :

A) For rivers, over Navigational High Flood Level (NHFL), which is the highest

Flood level at a frequency of 5% in any year over a period of last twenty

years

B) For tidal canals, over the highest high water level

C) For other canals, over designed for supply level

84

(The Official amendments to this document would bepublished by the IRC in its periodical, 'Indian Highways'which shall be considered as effective and as part of the

code/guidelines/manual, etc. from the date speciipied therein)

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